Vehicle height adjustment device

ABSTRACT

A vehicle height adjustment device includes a changer and a controller. The changer is configured to change a relative position of a body of a vehicle relative to an axle of a wheel of the vehicle. The controller is configured to control the changer to make the relative position a target value so as to control a vehicle height of the body of the vehicle. The controller is configured to control the changer to maintain the relative position irrespective of the target value when a decreasing malfunction occurs causing the vehicle height to decrease.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese Patent ApplicationNo. 2015-065984, filed Mar. 27, 2015 the entire contents of which areincorporated herein by reference.

BACKGROUND

Field of the Invention

The present invention relates to a vehicle height adjustment device.

Related Art

Japanese Examined Patent Publication No. 8-22680 discloses a vehicleheight adjustment device that increases the height of a motorcycleduring travel and that decreases the height of the motorcycle duringhalt in order to facilitate a rider's or a passenger's getting on andoff the motorcycle.

The vehicle height adjustment device automatically changes the height ofthe motorcycle in response to its speed of travel. Specifically, thevehicle height adjustment device automatically increases the height ofthe motorcycle when its speed reaches a set speed, and automaticallydecreases the height of the motorcycle when its speed changes to orbelow a set speed. In the adjustment of the height of the motorcycle, anelectromagnetic actuator is driven into operation.

SUMMARY

According to one aspect of the present disclosure, a vehicle heightadjustment device includes a changer and a controller. The changer isconfigured to change a relative position of a body of a vehicle relativeto an axle of a wheel of the vehicle. The controller is configured tocontrol the changer to make the relative position a target value so asto control a vehicle height of the body of the vehicle. The controlleris configured to control the changer to maintain the relative positionirrespective of the target value when a decreasing malfunction occurscausing the vehicle height to decrease.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present invention and many of theattendant advantages thereof will be readily obtained as the samebecomes better understood by reference to the following detaileddescription when considered in connection with the accompanyingdrawings, wherein:

FIG. 1 illustrates a schematic configuration of a motorcycle accordingto an embodiment;

FIG. 2 is a cross-sectional view of a front fork according to theembodiment;

FIG. 3 is an enlarged view of part III illustrated in FIG. 2;

FIG. 4 is an enlarged view of part IV illustrated in FIG. 3;

FIG. 5 illustrates how the front fork operates at the time of acompression stroke;

FIG. 6 illustrates how the front fork operates at the time of a reboundstroke;

FIG. 7 illustrates a flow of oil in a front-wheel passage switch unit ina first switch state;

FIG. 8 illustrates a flow of oil in the front-wheel passage switch unitin a second switch state;

FIG. 9 illustrates a flow of oil in the front-wheel passage switch unitin a third switch state;

FIG. 10 illustrates a flow of oil in the front-wheel passage switch unitin a fourth switch state;

FIG. 11A illustrates whether a first communication passage, a secondcommunication passage, and a third communication passage are open orclosed when the front-wheel passage switch unit is in the first switchstate;

FIG. 11B illustrates whether the first communication passage, the secondcommunication passage, and the third communication passage are open orclosed when the front-wheel passage switch unit is in the second switchstate;

FIG. 11C illustrates whether the first communication passage, the secondcommunication passage, and the third communication passage are open orclosed when the front-wheel passage switch unit is in the third switchstate;

FIG. 12 is a block diagram of a controller;

FIG. 13 is a block diagram of a passage switch unit controller;

FIG. 14A is a time chart illustrating an exemplary occurrence that isdue to a malfunction of a front-wheel relative position detector;

FIG. 14B is a time chart illustrating control details of a malfunctiondetector according to the embodiment; and

FIG. 15 is a flowchart of a procedure for control processing performedby the malfunction detector.

DESCRIPTION OF THE EMBODIMENTS

The embodiments will now be described with reference to the accompanyingdrawings, wherein like reference numerals designate corresponding oridentical elements throughout the various drawings.

FIG. 1 illustrates a schematic configuration of a motorcycle 1 accordingto this embodiment.

The motorcycle 1 includes a front wheel 2, a rear wheel 3, and a body10. The front wheel 2 is a wheel on the front side of the motorcycle 1.The rear wheel 3 is a wheel on the rear side of the motorcycle 1. Thebody 10 includes elements such as a frame 11, a handle 12, an engine 13,and a seat 19. The frame 11 defines the framework of the motorcycle 1.

The motorcycle 1 includes two front forks 21. One of the front forks 21is on the right side of the front wheel 2, and the other one of thefront forks 21 is on the left side of the front wheel 2. The front forks21 are examples of a suspension device that couples the front wheel 2and the body 10 to each other. The motorcycle 1 includes two rearsuspensions 22. One of the rear suspensions 22 is on the right side ofthe rear wheel 3, and the other one of the rear suspensions 22 is on theleft side of the rear wheel 3. The rear suspensions 22 couple the rearwheel 3 and the body 10 to each other. FIG. 1 illustrates only the frontfork 21 and the rear suspension 22 that are on the right side of themotorcycle 1. The front fork 21 and the rear suspension 22 are anexample of the changer to change the position of the body 10 relative tothe axle of the front wheel 2 and the position of the body 10 relativeto the axle of the rear wheel 3.

The motorcycle 1 includes two brackets 14 and a shaft 15. The shaft 15is disposed between the two brackets 14. The two brackets 14respectively hold the front fork 21 on the right side of the front wheel2 and the front fork 21 on the left side of the front wheel 2. The shaft15 is rotatably supported by the frame 11.

The motorcycle 1 includes a controller 70. The controller 70 controlsthe height of the motorcycle 1 by controlling a front-wheel passageswitch unit 300, described later, of each front fork 21 and a rear-wheelpassage switch unit 302, described later, of each rear suspension 22.The front-wheel passage switch unit 300 and the rear-wheel passageswitch unit 302 are non-limiting examples of an actuator.

The motorcycle 1 also includes a front-wheel rotation detection sensor31 and a rear-wheel rotation detection sensor 32. The front-wheelrotation detection sensor 31 detects the rotation angle of the frontwheel 2. The rear-wheel rotation detection sensor 32 detects therotation angle of the rear wheel 3.

Configuration of Front Fork 21

Each front fork 21 will be described in detail below.

FIG. 2 is a cross-sectional view of the front fork 21 according to thisembodiment.

The front fork 21 according to this embodiment is what is called anupright front fork that is disposed between the body 10 and the frontwheel 2 of the motorcycle 1 so as to support the front wheel 2. Theupright front fork 21 includes an outer member 110 (detailed later) andan inner tube 210 (detailed later). The outer member 110 is disposed onthe side of the front wheel 2, and the inner tube 210 is disposed on theside of the body 10.

The front fork 21 includes an axle side unit 100 and a body side unit200. The axle side unit 100 includes the outer member 110 and is mountedon the axle of the front wheel 2. The body side unit 200 includes theinner tube 210 and is mounted on the body 10. The front fork 21 alsoincludes a front-wheel spring 500. The front-wheel spring 500 isdisposed between the axle side unit 100 and the body side unit 200 toabsorb vibrations transmitted to the front wheel 2 caused by theroughness of a ground surface.

The outer member 110 and the inner tube 210 are coaxial, hollowcylindrical members. A direction of the center line (that is, an axialdirection) of each cylinder will be hereinafter occasionally referred toas “vertical direction”. In this case, the body 10 side willoccasionally be referred to the upper side, and the front wheel 2 sidewill occasionally be referred to as the lower side. By moving the axleside unit 100 and the body side unit 200 relative to each other in thevertical direction (axial direction), the front fork 21 absorbsvibrations caused by the roughness of the ground surface whilesupporting the front wheel 2.

Configuration of Axle Side Unit 100

The axle side unit 100 includes the outer member 110, an attenuationforce generation unit 130, a rod 150, and a rod holding member 160. Theouter member 110 is mounted on the axle of the front wheel 2. Theattenuation force generation unit 130 generates attenuation forceutilizing viscous resistance of oil. The rod 150 holds the attenuationforce generation unit 130. The rod holding member 160 holds thelower-side end of the rod 150.

The axle side unit 100 also includes a ball 166 and a regulation member167. The ball 166 has a spherical shape and is disposed in an axialdepression 161 a, described later, of the rod holding member 160. Theregulation member 167 regulates the movement of the ball 166.

The axle side unit 100 also includes a spring support member 170, asupport-member holding member 180, and a guide member 190. The springsupport member 170 supports the lower-side end of the front-wheel spring500. The support-member holding member 180 holds the spring supportmember 170. The guide member 190 guides the inner tube 210 to move inthe axial direction.

Configuration of Outer Member 110

The outer member 110 includes a hollow cylindrical portion 111 and anaxle bracket 112. The hollow cylindrical portion 111 has a hollowcylindrical shape for the inner tube 210 to be inserted into the hollowcylindrical shape. The axle bracket 112 is mountable to the axle of thefront wheel 2.

The hollow cylindrical portion 111, at its upper end, includes an oilseal 113 and a slide bush 114. The oil seal 113 seals the gap betweenthe outer surface of the inner tube 210 and the hollow cylindricalportion 111. The slide bush 114 smoothens the sliding contact betweenthe hollow cylindrical portion 111 and the outer surface of the innertube 210.

The axle bracket 112 has an axial through hole 112 a and an axlemounting hole 112 b. The axial through hole 112 a is oriented in theaxial direction for the rod holding member 160 to be inserted throughthe axial through hole 112 a. The axle mounting hole 112 b penetratesthe axle bracket 112 in a direction crossing the axial direction toreceive the axle of the front wheel 2.

Configuration of Attenuation Force Generation Unit 130

The attenuation force generation unit 130 includes a piston 131, anupper-end side valve 136, and a lower-end side valve 137. The piston 131defines an operating oil chamber 50, which is formed in the space insidea cylinder 230, described later. The upper-end side valve 136 isdisposed at the upper-side end of the piston 131. The lower-end sidevalve 137 is disposed at the lower-side end of the piston 131. Theattenuation force generation unit 130 also includes a piston bolt 140and a nut 145. The piston bolt 140 supports the piston 131, theupper-end side valve 136, the lower-end side valve 137, and othermembers. The nut 145 is screwed on the piston bolt 140 to determine thepositions of the piston 131, the upper-end side valve 136, the lower-endside valve 137, and other members.

The piston 131 is a hollow cylindrical member and has on its outersurface a hermetic member sealing the gap between the cylinder 230 andthe piston 131. The piston 131 also has a first through hole 132 and asecond through hole 133, which are through holes open in the axialdirection. The piston 131 includes first radial conduits 134 and secondradial conduits 135. The first radial conduits 134 radially extend atthe upper-side end of the piston 131 and communicate with the firstthrough hole 132. The second radial conduits 135 radially extend at thelower-side end of the piston 131 and communicate with the second throughhole 133. A non-limiting example of the number of each of the firstthrough holes 132 and the second through holes 133 is three. The threefirst through holes 132 and the three second through holes 133 are eachdisposed at equal intervals in a circumferential direction and atpositions respectively corresponding to the first through hole 132 andthe second through hole 133.

The upper-end side valve 136 is made up of a stack of approximatelydisk-shaped metal plates. A through hole penetrates the center of thestack of metal plates. A shaft 141, described later, of the piston bolt140 is inserted through the through hole. The upper-end side valve 136blocks the second through hole 133 and opens the first through hole 132.

The lower-end side valve 137 is made up of a stack of approximatelydisk-shaped metal plates. A through hole penetrates the center of thestack of metal plates. The shaft 141, described later, of the pistonbolt 140 is inserted through the through hole. The lower-end side valve137 blocks the first through hole 132 and opens the second through hole133.

The piston bolt 140 includes the shaft 141 and a base 142. The shaft 141is disposed on the upper end side of the piston bolt 140 and has a solidcylindrical shape. The base 142 is disposed on the lower end side of thepiston bolt 140 and has a solid cylindrical shape of larger radius thanthe radius of the shaft 141. In the piston bolt 140, a depression 143 isformed over the depth from the lower-side end surface of the base 142 tothe shaft 141.

The shaft 141 has a male thread formed at the upper-side end of theshaft 141. The male thread is screwed on a female thread formed on thenut 145.

The depression 143 has a female thread formed on the inner surface atthe lower-side end of the depression 143. The female thread receives amale thread formed on the upper-side end of the rod 150. At theupper-side end of the depression 143, a radial through hole 144 isformed. The radial through hole 144 radially penetrates the depression143 to allow the depression 143 to communicate with the outside of theshaft 141.

On the upper-side end of the nut 145, a female thread 146 is formed. Thefemale thread 146 receives a male thread of the piston bolt 140. Underthe female thread 146, a depression 147 is formed. The depression 147 isdepressed over a depth from the lower-side end surface of the nut 145,and has a solid cylindrical shape of larger radius than the radius ofthe root of the female thread 146. In the nut 145, a radial through hole148 is formed. The radial through hole 148 radially penetrates the nut145 to allow the outside of the nut 145 to communicate with thedepression 147.

With the configuration described hereinbefore, the attenuation forcegeneration unit 130 is held on the rod 150 with the male thread on theupper-side end of the rod 150 screwed on the female thread on thedepression 143 of the piston bolt 140. The piston 131 is in contact withthe inner surface of the cylinder 230 through the hermetic member on theouter surface of the piston 131. Thus, the piston 131 defines a firstoil chamber 51 and a second oil chamber 52 in the space inside thecylinder 230. The first oil chamber 51 is upper than the piston 131, andthe second oil chamber 52 is lower than the piston 131.

Configuration of Rod 150

The rod 150 is a hollow cylindrical member, and has male threads at theupper-side end and the lower-side end on the outer surface of the rod150. The male thread on the upper-side end of the rod 150 is screwed onthe piston bolt 140 of the attenuation force generation unit 130. Themale thread on the lower-side end of the rod 150 is screwed on a femalethread 161 d. The female thread 161 d is formed on an upper-end-sidesolid cylindrical portion 161. The upper-end-side solid cylindricalportion 161 is disposed on the upper end side of the rod holding member160. A lock nut 155 is screwed on the male thread on the lower-side endof the rod 150. Thus, the rod 150 is secured on the rod holding member160.

The rod 150 also has a female thread formed on the inner surface of therod 150 at the lower-side end of the rod 150.

Configuration of Rod Holding Member 160

The rod holding member 160 has a plurality of solid cylindrical portionsof different diameters. Namely, the rod holding member 160 includes theupper-end-side solid cylindrical portion 161, a lower-end-side solidcylindrical portion 162, and an intermediate solid cylindrical portion163. The upper-end-side solid cylindrical portion 161 is disposed at theupper-side end of the rod holding member 160. The lower-end-side solidcylindrical portion 162 is disposed at the lower-side end of the rodholding member 160. The intermediate solid cylindrical portion 163 isdisposed between the upper-end-side solid cylindrical portion 161 andthe lower-end-side solid cylindrical portion 162.

The upper-end-side solid cylindrical portion 161 has the axialdepression 161 a, a radial depression 161 b, and a radial through hole161 c. The axial depression 161 a is depressed over a depth in the axialdirection from the upper-side end surface of the upper-end-side solidcylindrical portion 161. The radial depression 161 b is depressedradially throughout the circumference of the upper-end-side solidcylindrical portion 161 over a depth from the outer surface of theupper-end-side solid cylindrical portion 161. The radial through hole161 c penetrates the axial depression 161 a and the radial depression161 b in a radial direction.

The axial depression 161 a has the female thread 161 d, which receivesthe male thread on the lower-side end of the rod 150. The axialdepression 161 a also has an inclined surface 161 e. The inclinedsurface 161 e is inclined relative to the axial direction, that is, theinner diameter of the inclined surface 161 e gradually decreases in thelower side direction.

On the lower-side end of the upper-end-side solid cylindrical portion161, a male thread 161 f is formed. The male thread 161 f is screwed ona female thread 181, which is described later and formed on thesupport-member holding member 180.

The intermediate solid cylindrical portion 163 has a diameter smallerthan the inner diameter of the axial through hole 112 a of the outermember 110. Thus, the intermediate solid cylindrical portion 163 isfitted in the axial through hole 112 a of the outer member 110.

On the outer surface of the lower-end-side solid cylindrical portion162, a male thread 162 a is formed.

The rod holding member 160 is secured on the outer member 110 with themale thread 162 a, which is on the lower-end-side solid cylindricalportion 162, screwed on a nut 165. The nut 165 is inserted through theaxial through hole 112 a of the outer member 110.

Configuration of Regulation Member 167

The regulation member 167 is a stepped, hollow cylindrical member. Theregulation member 167 has a male thread formed on the outer surface atthe upper-side end of the regulation member 167. The regulation member167 is secured on the rod 150 with the male thread screwed on the femalethread on the inner surface at the lower-side end of the rod 150. Theregulation member 167, at its lower-side end, regulates the movement ofthe ball 166, which is disposed in the axial depression 161 a of the rodholding member 160.

Configuration of Spring Support Member 170

The spring support member 170 is a hollow cylindrical member, and issecured on the upper-side end of the support-member holding member 180.Examples of the method of securing the spring support member 170include, but are not limited to, welding and press fitting.

Configuration of Support-Member Holding Member 180

The support-member holding member 180 is a hollow cylindrical member. Atthe lower-side end of the support-member holding member 180, the femalethread 181 is formed. The female thread 181 receives the male thread 161f, which is formed on the rod holding member 160. The support-memberholding member 180 is secured on the rod holding member 160 with thefemale thread 181 receiving the male thread 161 f, which is formed onthe rod holding member 160. The support-member holding member 180 has acommunication hole 182. The communication hole 182 is formed at aposition axially corresponding to the radial depression 161 b of the rodholding member 160, and thus communicates the inside and outside of thesupport-member holding member 180 with each other.

Configuration of Guide Member 190

The guide member 190 includes a hollow cylindrical portion 191 and aninternally facing portion 192. The hollow cylindrical portion 191 has ahollow cylindrical shape. The internally facing portion 192 radiallyinternally extends from the lower-side end of the hollow cylindricalportion 191.

The guide member 190 is secured between the rod holding member 160 andthe outer member 110 with the internally facing portion 192 held betweenthe rod holding member 160 and the outer member 110.

The internally facing portion 192 is chamfered at the lower-side end ofthe internally facing portion 192. An O ring 195 is fitted in the spacedefined between the chamfered portion and the rod holding member 160.The O ring 195 seals the gap between the guide member 190, the rodholding member 160, and the outer member 110. Thus, the O ring 195 keepsthe space inside the hollow cylindrical portion 111 of the outer member110 liquid tight.

In the axle side unit 100 with the configuration described hereinbefore,a reservoir chamber 40 (storage chamber) is defined between the innersurface of the outer member 110 and the outer surfaces of the rod 150and the support-member holding member 180. The reservoir chamber 40stores oil kept hermetic in the front fork 21.

Configuration of Body Side Unit 200

The body side unit 200 includes the inner tube 210 and a cap 220. Theinner tube 210 has a hollow cylindrical shape with open ends. The cap220 is mounted on the upper-side end of the inner tube 210.

The body side unit 200 also includes the cylinder 230 and a hermeticmember 240. The cylinder 230 has a hollow cylindrical shape. Thehermetic member 240 is mounted on the lower-side end of the cylinder230, and keeps the space inside the cylinder 230 hermetic.

The body side unit 200 also includes a front-wheel spring lengthadjustment unit 250 and the front-wheel passage switch unit 300. Thefront-wheel spring length adjustment unit 250 is a non-limiting exampleof the adjustor that supports the front-wheel spring 500 at itsupper-side end and adjusts (changes) the length of the front-wheelspring 500. The front-wheel passage switch unit 300 is mounted on theupper-side end of the cylinder 230 and selects a passage for oil, whichis a non-limiting example of the fluid.

The body side unit 200 also includes a front-wheel relative positiondetector 281 (which is the detector) (see FIGS. 11A to 11C). Thefront-wheel relative position detector 281 detects the position of anupper-side end support member 270 relative to a base member 260,described later, of the front-wheel spring length adjustment unit 250.

Configuration of Inner Tube 210

The inner tube 210 is a hollow cylindrical member.

The inner tube 210, at its lower-side end, includes a slide bush 211 anda movement regulation member 212. The slide bush 211 has a hollowcylindrical shape and smoothens the sliding contact between the innertube 210 and the inner surface of the hollow cylindrical portion 111 ofthe outer member 110. The movement regulation member 212 has a hollowcylindrical shape and is in contact with the spring support member 170and the axle bracket 112 of the outer member 110. Thus, the movementregulation member 212 regulates axial movement of the inner tube 210.

On the upper-side end of the inner tube 210, a female thread 213 isformed. The female thread 213 receives a male thread formed on the cap220, described later.

Configuration of Cap 220

The cap 220 is an approximately hollow cylindrical member. On the outersurface of the cap 220, a male thread 221 is formed. The male thread 221is screwed on the female thread 213, which is formed on the inner tube210. On the inner surface of the cap 220, a female thread is formed thatreceives male threads on the front-wheel spring length adjustment unit250 and the front-wheel passage switch unit 300. The cap 220 is mountedon the inner tube 210 and holds the front-wheel spring length adjustmentunit 250 and the front-wheel passage switch unit 300.

The cap 220 includes an O ring 222. The O ring 222 keeps the spaceinside the inner tube 210 liquid tight.

Configuration of Cylinder 230

The cylinder 230 is a hollow cylindrical member. On the outer surface atthe upper-side end of the cylinder 230, a female thread is formed thatreceives the male thread on the front-wheel passage switch unit 300. Onthe inner surface at the lower-side end of the cylinder 230, a femalethread is formed that receives a male thread on the hermetic member 240.

Configuration of Hermetic Member 240

The hermetic member 240 is a hollow cylindrical member. On the outersurface of the hermetic member 240, a male thread is formed that isscrewed on the female thread on the inner surface at the lower-side endof the cylinder 230. The hermetic member 240 is held on the cylinder 230with the male thread screwed on the female thread on the inner surfaceat the lower-side end of the cylinder 230.

The hermetic member 240 includes a slide bush 245 on the innercircumference side of the hermetic member 240. The slide bush 245smoothens the sliding contact between the hermetic member 240 and theouter surface of the rod 150. In order to keep the space inside thecylinder 230 liquid tight, the hermetic member 240 includes an O ring246 and an O ring 247. The O ring 246 is disposed between the hermeticmember 240 and the outer surface of the rod 150. The O ring 247 isdisposed between the hermetic member 240 and the inner surface of thecylinder 230.

The hermetic member 240 also includes an impact alleviation member 248at the upper-side end of the hermetic member 240. The impact alleviationmember 248 alleviates the impact of contact between the hermetic member240 and the attenuation force generation unit 130. A non-limitingexample of the impact alleviation member 248 is an elastic member suchas resin and rubber.

Configuration of Front-Wheel Spring Length Adjustment Unit 250

The front-wheel spring length adjustment unit 250 includes the basemember 260 and the upper-side end support member 270. The base member260 is secured on the cap 220. The upper-side end support member 270supports the front-wheel spring 500 at its upper-side end, and ismovable in the axial direction relative to the base member 260. Thus,the upper-side end support member 270 adjusts the length of thefront-wheel spring 500.

The base member 260 is an approximately hollow cylindrical member. Onthe outer surface at the upper-side end of the base member 260, a malethread 260 a is formed. The male thread 260 a is screwed on the femalethread on the cap 220. The base member 260 is secured on the cap 220with the male thread 260 a screwed on the female thread on the cap 220.

The base member 260 has a protrusion 260 b at the upper-side end of thebase member 260. The protrusion 260 b is a radially protruding part ofthe circumference of the base member 260. A discharge passage 41 isdisposed between the protrusion 260 b and the lower-side end on theouter surface of a support member 400, described later. The dischargepassage 41 is for the oil in the cylinder 230 to be discharged into thereserver chamber 40.

The base member 260, at its lower-side end, includes a slide bush 261and an O ring 262. The slide bush 261 has a hollow cylindrical shapefitted in the outer circumference of the base member 260, and smoothensthe sliding contact between the base member 260 and the inner surface ofthe upper-side end support member 270. The O ring 262 is radially innerthan the slide bush 261. A ring-shaped passage 61 is defined between theinner surface of the base member 260 and the outer surface of thecylinder 230. The ring-shaped passage 61 has a ring shape.

The upper-side end support member 270 includes a hollow cylindricalportion 271 and an internally facing portion 272. The hollow cylindricalportion 271 has a hollow cylindrical shape. The internally facingportion 272 radially internally extends from the lower-side end of thehollow cylindrical portion 271. The upper-side end support member 270defines a jack chamber 60 in the space defined between the outer surfaceof the cylinder 230 and the lower-side end of the base member 260. Thejack chamber 60 stores oil for use in adjusting the position of theupper-side end support member 270 relative to the base member 260.

The hollow cylindrical portion 271 has an inner diameter equal to orsmaller than the outer diameter of the slide bush 261, which is fittedin the base member 260. The hollow cylindrical portion 271 has a radialthrough hole 273. The radial through hole 273 radially penetrates thehollow cylindrical portion 271 and thus communicates the inside andoutside of the hollow cylindrical portion 271 with each other. Throughthe radial through hole 273, the oil in the jack chamber 60 isdischarged into the reservoir chamber 40. In this manner, thedisplacement of the upper-side end support member 270 relative to thebase member 260 is regulated.

The internally facing portion 272 includes an O ring 274 on the innercircumference side of the internally facing portion 272. The O ring 274seals the gap between the internally facing portion 272 and the outersurface of the cylinder 230, and thus keeps the jack chamber 60 liquidtight.

The jack chamber 60 is supplied the oil in the cylinder 230 through thering-shaped passage 61, which is defined between the inner surface ofthe base member 260 and the outer surface of the cylinder 230. Thisconfiguration will be detailed later.

Configuration of Front-Wheel Relative Position Detector 281

The front-wheel relative position detector 281 detects, for example, theamount of displacement of the upper-side end support member 270 in thevertical direction relative to the base member 260, that is, the amountof displacement of the upper-side end support member 270 in the verticaldirection relative to the body frame 11. In a non-limiting embodiment, acoil is wound around the outer surface of the base member 260, and theupper-side end support member 270 is made of magnetic material. Based onthe impedance of the coil, which changes in accordance with displacementof the upper-side end support member 270 in the vertical directionrelative to the base member 260, the front-wheel relative positiondetector 281 detects the amount of displacement of the upper-side endsupport member 270.

Configuration of Front-Wheel Passage Switch Unit 300

FIG. 3 is an enlarged view of part III illustrated in FIG. 2.

FIG. 4 is an enlarged view of part IV illustrated in FIG. 3.

The front-wheel passage switch unit 300 is a device that switches amonga first option, a second option, and a third option. In the firstoption, the front-wheel passage switch unit 300 supplies oil dischargedfrom a pump 600, described later, to the reservoir chamber 40. In thesecond option, the front-wheel passage switch unit 300 supplies the oildischarged from the pump 600 to the jack chamber 60. In the thirdoption, the front wheel passage switch unit 300 supplies the oilaccommodated in the jack chamber 60 to the reservoir chamber 40.

The front-wheel passage switch unit 300 includes a front-wheel solenoid310, a spherical valve body 321, a push rod 322, a valve-body seatmember 330, a coil spring 340, and a press member 350. The push rod 322presses the valve body 321. The valve-body seat member 330 has a restingsurface for the valve body 321. The press member 350 receives the springforce of the coil spring 340 to press the valve body 321 against theresting surface.

The front-wheel passage switch unit 300 also includes a ball 360, a coilspring 361, and a disc 362. The coil spring 361 applies axial urgingforce to the ball 360. The disc 362 is disposed between the ball 360 andthe coil spring 361. The front-wheel passage switch unit 300 alsoincludes a ball seat member 365 and an accommodation member 370. Theball seat member 365 has a resting surface for the ball 360. Theaccommodation member 370 accommodates the coil spring 361 and the disc362.

The front-wheel passage switch unit 300 also includes a valveaccommodation inner member 380, a valve accommodation outer member 390,and the support member 400. The valve accommodation inner member 380accommodates the valve body 321, the valve-body seat member 330, andother members. The valve accommodation outer member 390 is disposedoutside the valve accommodation inner member 380, and accommodates theball 360, the ball seat member 365, and other members. The supportmember 400 supports the valve accommodation inner member 380 and thevalve accommodation outer member 390.

The front-wheel passage switch unit 300 also includes a transmissionmember 410 and a coil spring 415. The transmission member 410 is mountedon the lower end of an operation rod 314, described later, of thefront-wheel solenoid 310, and transmits thrust of the front-wheelsolenoid 310 to the push rod 322. The coil spring 415 applies axialurging force to the transmission member 410.

Configuration of Front-Wheel Solenoid 310

The front-wheel solenoid 310 is a proportional solenoid that includes acoil 311, a core 312, a plunger 313, and an operation rod 314. The core312 is disposed inside the coil 311. The plunger 313 is guided by thecore 312. The operation rod 314 is coupled to the plunger 313.

The front-wheel solenoid 310 also includes a case 315 and a cover 316.The case 315 accommodates the coil 311, the core 312, the plunger 313,and other members. The cover 316 covers an opening of the case 315.

The case 315 includes a hollow cylindrical portion 315 a and aninternally facing portion 315 b. The hollow cylindrical portion 315 ahas a hollow cylindrical shape. The internally facing portion 315 bradially internally extends from the lower-side end of the hollowcylindrical portion 315 a. The internally facing portion 315 b has athrough hole through which the operation rod 314 is inserted. A guidebush 315 c is fitted with the internally facing portion 315 b to guidethe movement of the operation rod 314.

The operation rod 314 has a hollow cylindrical shape. At the upper-sideend, the operation rod 314 is accommodated in the case 315. At thelower-side end, the operation rod 314 protrudes from the case 315. Theportion of the operation rod 314 protruding from the case 315 isattached with a disc-shaped valve 317. The disc-shaped valve 317 opensand closes a passage, described later, formed in the valve accommodationinner member 380. A coil spring 318 surrounds the portion of theoperation rod 314 between the valve 317 and the case 315. The coilspring 318 applies an axial urging force to the valve 317.

With the configuration of the front-wheel solenoid 310 describedhereinbefore, the coil 311 is supplied a current through a connector anda lead that are mounted on the cap 220. The current causes the plunger313 to generate an axial thrust that accords with the amount of thecurrent. The thrust of the plunger 313 causes the operation rod 314,which is coupled to the plunger 313, to make an axial movement. In thefront-wheel solenoid 310 according to this embodiment, the plunger 313generates an amount of axial thrust that causes the operation rod 314 toprotrude from the case 315 by an amount that increases as the currentsupplied to the coil 31 increases.

The amount of the current supplied to the coil 311 is controlled by thecontroller 70.

Configuration of Push Rod 322

As illustrated in FIG. 3, the push rod 322 includes a first shaft 322 a,a second shaft 322 b, and a third shaft 322 c. The first shaft 322 a hasa cylindrical shape and is disposed on the upper end side of the pushrod 322. The second shaft 322 b has a cylindrical shape and is disposedon the lower end side of the push rod 322. The third shaft 322 c has acylindrical shape and is disposed between the first shaft 322 a and thesecond shaft 322 b.

The third shaft 322 c has a radius larger than each radius of the firstshaft 322 a and the second shaft 322 b. In other words, across-sectional area of the third shaft 322 c perpendicular to the axialdirection is larger than a cross-sectional area of each of the firstshaft 322 a and the second shaft 322 b perpendicular to the axialdirection.

The valve body 321 and the push rod 322 may be integral to each other.

Configuration of Valve-Body Seat Member 330

The valve-body seat member 330 includes a conical portion 332 and asolid cylindrical portion 333. The conical portion 332 has an inclinedsurface 331. The inclined surface 331 is inclined relative to the axialdirection, that is, the outer diameter of the valve-body seat member 330gradually increases in the lower side direction. The solid cylindricalportion 333 has a solid cylindrical shape.

The conical portion 332 has an upper-end depression 334. The upper-enddepression 334 is depressed over a depth in the axial direction from theupper-side end surface of the conical portion 332. The solid cylindricalportion 333 has a lower-end depression 335 and a communication hole 336.The lower-end depression 335 is depressed over a depth in the axialdirection from the lower-side end surface of the solid cylindricalportion 333. Through the communication hole 336, the lower-enddepression 335 and the upper-end depression 334 communicate with eachother.

The upper-end depression 334 has an inner diameter larger than theradius of the third shaft 322 c. The communication hole 336 has an innerdiameter larger than the radius of the second shaft 322 b. The secondshaft 322 b and the third shaft 322 c in the push rod 322 are insertedin the communication hole 336 and the upper-end depression 334. The gapbetween the outer surface of the second shaft 322 b and the innersurface of the communication hole 336, and the gap between the outersurface of the third shaft 322 c and the inner surface of the upper-enddepression 334 function as part of a third communicating passage R3,described later, and part of a fourth communicating passage R4,described later.

The lower-end depression 335 includes a conical depression 335 b and acylindrical depression 335 c. The conical depression 335 b has aninclined surface 335 a. The inclined surface 335 a is inclined relativeto the axial direction, that is, the radius of the conical depression335 b gradually increases in the lower side direction. The cylindricaldepression 335 c has a cylindrical shape. The radius of the conicaldepression 335 b increases in the lower side direction from a valuesmaller than the radius of the valve body 321 to a value larger than theradius of the valve body 321. The conical depression 335 b accommodatesthe valve body 321. With the valve body 321 in contact with the inclinedsurface 335 a, the gap between the valve body 321 and the conicaldepression 335 b is sealed. The radius of the cylindrical depression 335c of the lower-end depression 335 is larger than the radius of a firstsolid cylindrical portion 351, described later, of the press member 350.The lower-end depression 335 accommodates the first solid cylindricalportion 351 of the press member 350.

The conical portion 332 has a groove 332 a on the outer surface of theconical portion 332. The groove 332 a is depressed radially throughoutthe circumference of the conical portion 332. An O ring 337 is fitted inthe groove 332 a to seal the gap between the conical portion 332 and thevalve accommodation inner member 380.

Configuration of Press Member 350

The press member 350 includes two solid cylindrical portions ofdifferent diameters, namely, the first solid cylindrical portion 351 andthe second solid cylindrical portion 352. The first solid cylindricalportion 351 has a depression formed on the upper-side end surface of thefirst solid cylindrical portion 351. This depression fits the shape ofthe lower-side end of the valve body 321. The radius of the first solidcylindrical portion 351 is larger than the radius of the valve body 321and larger than half the center diameter of the coil spring 340. On theupper-side end surface, the first solid cylindrical portion 351 supportsthe lower-side end of the valve body 321. On the lower-side end surface,the first solid cylindrical portion 351 supports the upper-side end ofthe coil spring 340.

The radius of the second solid cylindrical portion 352 is smaller thanhalf the inner diameter of the coil spring 340. The second solidcylindrical portion 352 is inside the coil spring 340.

Configuration of Ball Seat Member 365

The ball seat member 365 is a hollow cylindrical member with a flangeformed at the upper-side end of the ball seat member 365. The ball seatmember 365 has an opening at the upper-side end of the ball seat member365. In the opening, a depression is formed that fits the shape of thelower-side end of the ball 360. The ball seat member 365 has a groove366 formed on the outer surface of the ball seat member 365. The groove366 is depressed radially throughout the circumference of the ball seatmember 365. An O ring 367 is fitted in the groove 366 to seal the gapbetween the groove 366 and the valve accommodation outer member 390.

Configuration of Accommodation Member 370

The accommodation member 370 is an approximately solid cylindricalmember. The accommodation member 370 has an upper-end depression 371 anda lower-end depression 372. The upper-end depression 371 has acylindrical shape and is depressed over a depth in the axial directionfrom the upper-side end surface of the accommodation member 370. Thelower-end depression 372 has a cylindrical shape and is depressed over adepth in the axial direction from the lower-side end surface of theaccommodation member 370. The upper-end depression 371 accommodates thelower-side end of the coil spring 340. The lower-end depression 372accommodates the coil spring 361 and the disc 362. The opening of thelower-end depression 372 is larger in size than the upper-side end ofthe ball 360. The lower-end depression 372 accommodates the upper-sideend of the ball 360.

The accommodation member 370 is fitted in the lower-side end of thevalve accommodation inner member 380. On the outer surface of theaccommodation member 370, a groove 373 is formed. The groove 373 isdepressed radially throughout the circumference of the accommodationmember 370. An O ring 374 is fitted in the groove 373 to seal the gapbetween the accommodation member 370 and the valve accommodation innermember 380.

A radial through hole 375 is formed in a portion of the accommodationmember 370 exposed from the valve accommodation inner member 380. Theradial through hole 375 radially penetrates the accommodation member 370to allow the inside of the lower-end depression 372 to communicate withthe outside of the accommodation member 370.

Configuration of Valve Accommodation Inner Member 380

The valve accommodation inner member 380 is an approximately solidcylindrical member with a flange formed at the upper-side end of thevalve accommodation inner member 380. The valve accommodation innermember 380 has an upper-end depression 381, a lower-end depression 382,and a communication hole 383. The upper-end depression 381 is depressedover a depth in the axial direction from the upper-side end surface ofthe valve accommodation inner member 380. The lower-end depression 382is depressed over a depth in the axial direction from the lower-side endsurface of the valve accommodation inner member 380. Through thecommunication hole 383, the upper-end depression 381 and the lower-enddepression 382 communicate with each other.

On the outer surface of the valve accommodation inner member 380, afirst radial depression 384 and a second radial depression 385 areformed. The first radial depression 384 and the second radial depression385 are depressed radially throughout the circumference of the valveaccommodation inner member 380.

The upper-end depression 381 has a solid cylindrical shape thataccommodates the transmission member 410 and the coil spring 415.

The lower-end depression 382 includes a first cylindrical depression 382a, a second cylindrical depression 382 b, and a conical depression 382c. The first cylindrical depression 382 a and the second cylindricaldepression 382 b have cylindrical shapes of different diameters. Theconical depression 382 c is formed between the first cylindricaldepression 382 a and the second cylindrical depression 382 b, and has aninclined surface inclined relative to the axial direction, that is, theradius of the conical depression 382 c gradually increases in the lowerside direction.

The first cylindrical depression 382 a, the second cylindricaldepression 382 b, and the second cylindrical depression 382 baccommodate the valve-body seat member 330. Specifically, the inclinedsurface of the conical depression 382 c fits the shape of the inclinedsurface 331 of the conical portion 332 of the valve-body seat member330. The second cylindrical depression 382 b has a radius smaller thanthe radius of the solid cylindrical portion 333 of the valve-body seatmember 330.

The upper-side end of the accommodation member 370 is fitted in theopening of the lower-end depression 382, that is, the lower-side end ofthe second cylindrical depression 382 b. The O ring 374, which is fittedin the accommodation member 370, seals the gap between the accommodationmember 370 and the valve accommodation inner member 380.

An O ring 386 is fitted in the second radial depression 385 to seal thegap between the second radial depression 385 and the valve accommodationouter member 390.

The valve accommodation inner member 380 has a plurality of first radialcommunication holes 387, which are formed at equal intervals in thecircumferential direction. Each first radial communication hole 387 is aradial through hole through which the first cylindrical depression 382 aof the lower-end depression 382 and the first radial depression 384communicate with each other.

The valve accommodation inner member 380 has a plurality of secondradial communication holes 388, which are formed at equal intervals inthe circumferential direction. Each second radial communication hole 388is a radial through hole through which the second cylindrical depression382 b and the outside of the valve accommodation inner member 380communicate with each other.

The valve accommodation inner member 380 has a plurality of inner axialcommunication holes 389 a formed at equal intervals in thecircumferential direction. Each inner axial communication hole 389 a isan axial through hole through which the upper-side end of the valveaccommodation inner member 380 and the first radial depression 384communicate with each other.

The valve accommodation inner member 380 has a plurality of outer axialcommunication holes 389 b formed at equal intervals in thecircumferential direction. The outer axial communication holes 389 baxially penetrate the flange.

Configuration of Valve Accommodation Outer Member 390

The valve accommodation outer member 390 includes a first hollowcylindrical portion 391, a second hollow cylindrical portion 392, and aflange. The first hollow cylindrical portion 391 and the second hollowcylindrical portion 392 have cylindrical shapes of different diameters.The flange extends radially outwardly from the upper-side end of thefirst hollow cylindrical portion 391. The first hollow cylindricalportion 391 has an outer diameter larger than the outer diameter of thesecond hollow cylindrical portion 392.

The valve accommodation outer member 390 has an upper-end depression393. The upper-end depression 393 is depressed over a depth in the axialdirection from the upper-side end surface of the valve accommodationouter member 390.

The first hollow cylindrical portion 391 has a plurality of axialcommunication holes 394, which are formed at equal intervals in thecircumferential direction. Each axial communication hole 394 allows theupper-end depression 393 to communicate with the space that is below thefirst hollow cylindrical portion 391 and defined between the outersurface of the second hollow cylindrical portion 392 and the innersurface of the cylinder 230.

The first hollow cylindrical portion 391 has, on its outer surface, afirst radial depression 395, a second radial depression 396, and a malethread 390 a. The first radial depression 395 and the second radialdepression 396 are depressed radially throughout the circumference ofthe first hollow cylindrical portion 391. The male thread 390 a isscrewed on the female thread at the upper-side end of the cylinder 230.

An O ring 395 a is fitted in the first radial depression 395 to seal thegap between the first radial depression 395 and the base member 260 ofthe front-wheel spring length adjustment unit 250.

An O ring 396 a is fitted in the second radial depression 396 to sealthe gap between the second radial depression 396 and the cylinder 230.

The first hollow cylindrical portion 391 has a plurality of first radialcommunication holes 397 and a plurality of second radial communicationholes 398. The first radial communication holes 397 and the secondradial communication holes 398 are radial through holes that allow theinside and outside of the first hollow cylindrical portion 391 tocommunicate with each other. The first radial communication holes 397and the second radial communication holes 398 are formed at equalintervals in the circumferential direction and at positions on the firsthollow cylindrical portion 391 where no axial communication holes 394are formed. Specifically, the first radial communication holes 397 areat positions upper in the axial direction than the positions of thefirst radial depression 395, and the second radial communication holes398 are formed between the first radial depression 395 and the secondradial depression 396 in the axial direction.

The second hollow cylindrical portion 392 has a protrusion 399. Theprotrusion 399 radially internally protrudes from the inner surface ofthe second hollow cylindrical portion 392. The flange of the ball seatmember 365 is mounted on the upper-side end surface of the protrusion399. The gap between the inner surface of the protrusion 399 and theouter surface of the ball seat member 365 is sealed by the O ring 367,which is fitted in the ball seat member 365.

The cylinder 230 is held on the valve accommodation outer member 390with the male thread 390 a on the outer surface of the first hollowcylindrical portion 391 screwed on the female thread on the innersurface of the cylinder 230.

Configuration of Support Member 400

As illustrated in FIG. 3, the support member 400 includes a hollowcylindrical portion 401 and an internally facing portion 402. The hollowcylindrical portion 401 has a hollow cylindrical shape. The internallyfacing portion 402 radially internally extends from the lower-side endof the hollow cylindrical portion 401.

On the outer surface at the upper-side end of the hollow cylindricalportion 401, a male thread 403 is formed. The male thread 403 is screwedon the female thread on the cap 220. The support member 400 is held onthe cap 220 with the male thread 403, which is formed on the outersurface of the hollow cylindrical portion 401, screwed on the femalethread on the cap 220. The support member 400 holds the valveaccommodation inner member 380 and the valve accommodation outer member390 by holding the flange of the valve accommodation inner member 380and the flange of the valve accommodation outer member 390 between theinternally facing portion 402 and the front-wheel solenoid 310.

Configuration of Transmission Member 410

The transmission member 410 includes a first solid cylindrical portion411 and a second solid cylindrical portion 412. The first solidcylindrical portion 411 and the second solid cylindrical portion 412have solid cylindrical shapes of different diameters.

The second solid cylindrical portion 412 has an outer diameter smallerthe inner diameter of the coil spring 415, and thus the second solidcylindrical portion 412 is inserted in the coil spring 415.

The first solid cylindrical portion 411 has an outer diameter largerthan the inner diameter of the coil spring 415. The first solidcylindrical portion 411 has a groove formed on the outer surface of thefirst solid cylindrical portion 411. The upper-side end of the coilspring 415 is fitted in the groove.

The transmission member 410 and the coil spring 415 are accommodated inthe upper-end depression 381 of the valve accommodation inner member380.

The valve 317 and the coil spring 318 are accommodated in a depression319, which is formed on the lower-side end surface of the front-wheelsolenoid 310. The valve 317 has an axial through hole 317 a. The axialthrough hole 317 a is formed at a position facing the upper-enddepression 381 of the valve accommodation inner member 380. The coilspring 318 applies, to the valve 317, axial urging force directed towardthe upper-side end surface of the valve accommodation inner member 380.

With the configuration of the front-wheel passage switch unit 300described hereinbefore, when supply of current to the coil 311 of thefront-wheel solenoid 310 is stopped or when the current supplied to thecoil 311 is less than a predetermined first reference current, the valve317, which is mounted on the operation rod 314, does not rest on theupper-side end surface of the valve accommodation inner member 380. Thisreleases open the opening on the upper end side of the inner axialcommunication hole 389 a, which is formed in the valve accommodationinner member 380.

When the current supplied to the coil 311 of the front-wheel solenoid310 is equal to or higher than the first reference current, theoperation rod 314 moves in the lower side direction to make the valve317, which is mounted on the operation rod 314, rest on the upper-sideend surface of the valve accommodation inner member 380 to close theopening on the upper end side of the inner axial communication hole 389a.

When the current supplied to the coil 311 of the front-wheel solenoid310 is equal to or higher than a predetermined second reference current,which is higher than the first reference current, the operation rod 314moves further in the lower side direction. Then, the operation rod 314pushes the push rod 322 in the lower side direction through thetransmission member 410. When the push rod 322 is pushed in the lowerside direction, the valve body 321 is pushed by the push rod 322 awayfrom the inclined surface 335 a of the lower-end depression 335 of thevalve-body seat member 330.

When the supply of current to the coil 311 is stopped or when thecurrent supplied to the coil 311 is less than the first referencecurrent, the valve 317, which is mounted on the operation rod 314,releases the inner axial communication hole 389 a, which is formed inthe valve accommodation inner member 380, and the valve body 321 restson the inclined surface 335 a of the lower-end depression 335 of thevalve-body seat member 330. This state will be hereinafter referred toas first switch state.

When the current supplied to the coil 311 is equal to or higher than thefirst reference current and less than the second reference current, thevalve 317, which is mounted on the operation rod 314, closes the inneraxial communication hole 389 a, which is formed in the valveaccommodation inner member 380, and the valve body 321 rests on theinclined surface 335 a of the lower-end depression 335 of the valve-bodyseat member 330. This state will be hereinafter referred to as secondswitch state.

When the current supplied to the coil 311 is equal to or higher than thesecond reference current and less than a third reference current, thevalve 317, which is mounted on the operation rod 314, closes the inneraxial communication hole 389 a, which is formed in the valveaccommodation inner member 380, and the valve body 321 is away from theinclined surface 335 a of the lower-end depression 335 of the valve-bodyseat member 330. This state will be hereinafter referred to as thirdswitch state.

In a non-limiting example, the first reference current and the secondreference current are respectively 0.1 A and 0.5 A. A non-limitingexample of the maximum current flowing to the coil 311 of thefront-wheel solenoid 310 is 2 A.

When the current supplied to the coil 311 is equal to or higher than thethird reference current, the valve 317, which is mounted on theoperation rod 314, closes the inner axial communication hole 389 a,which is formed in the valve accommodation inner member 380, and theinclined surface 331 of the conical portion 332 of the valve-body seatmember 330 is away from the inclined surface on the conical depression382 c of the valve accommodation inner member 380. This state will behereinafter referred to as fourth switch state. In the fourth switchstate, the valve body 321 rests on the inclined surface 335 a of thelower-end depression 335 of the valve-body seat member 330.

Operation of Front Fork 21

With the configuration of the front fork 21 described hereinbefore, thefront-wheel spring 500 supports the weight of the motorcycle 1 and thusabsorbs impact. The attenuation force generation unit 130 attenuates thevibration in the front-wheel spring 500.

FIG. 5 illustrates how the front fork 21 operates at the time of acompression stroke.

In the compression stroke of the front fork 21, the piston 131 of theattenuation force generation unit 130 moves in the upper-side directionrelative to the cylinder 230 as indicated by the outlined arrow. Themovement of the piston 131 causes the oil in the first oil chamber 51 tobe pressurized. This causes the lower-end side valve 137 covering thefirst through hole 132 to open and the oil to flow into the second oilchamber 52 through the first through hole 132 (see arrow C1). The oilflow from the first oil chamber 51 to the second oil chamber 52 isnarrowed through the first through hole 132 and the lower-end side valve137. This causes attenuation force for the compression stroke to begenerated.

At the time of the compression stroke, the rod 150 enters the cylinder230. The entry causes an amount of oil corresponding to the volume ofthe rod 150 in the cylinder 230 to be supplied to the jack chamber 60 orthe reservoir chamber 40, which depends on the switch state selected bythe front-wheel passage switch unit 300 (see arrow C2). The switch stateselected by the front-wheel passage switch unit 300 as to which of thejack chamber 60 and the reservoir chamber 40 to supply the oil will bedescribed later. Here, the attenuation force generation unit 130, therod 150, the cylinder 230, and other elements function as a pump tosupply the oil in the cylinder 230 to the jack chamber 60 or thereservoir chamber 40. In the following description, this pump willoccasionally be referred to as “pump 600”.

FIG. 6 illustrates how the front fork 21 operates at the time of arebound stroke.

In the rebound stroke of the front fork 21, the piston 131 of theattenuation force generation unit 130 moves in the lower-side directionrelative to the cylinder 230 as indicated by the outlined arrow. Themovement of the piston 131 causes the oil in the second oil chamber 52to be pressurized. This causes the upper-end side valve 136 covering thesecond through hole 133 to open and the oil to flow into the first oilchamber 51 through the second through hole 133 (see arrow T1). The oilflow from the second oil chamber 52 to the first oil chamber 51 isnarrowed through the second through hole 133 and the upper-end sidevalve 136. This causes attenuation force for the rebound stroke to begenerated.

At the time of the rebound stroke, the rod 150 withdraws from thecylinder 230. The withdrawal causes an amount of oil corresponding tothe volume of the rod 150 that has been in the cylinder 230 to besupplied from the reservoir chamber 40 to the first oil chamber 51. Thatis, the movement of the piston 131 in the lower-side direction causesthe first oil chamber 51 to be depressurized and the oil in thereservoir chamber 40 to enter the first oil chamber 51. Specifically,the oil in the reservoir chamber 40 passes through the communicationhole 182 of the support-member holding member 180 and the radial throughhole 161 c of the rod holding member 160, and enters the axialdepression 161 a of the rod holding member 160. Then, the oil moves theball 166 in the upper-side direction and enters the rod 150 (see arrowT2). In the rod 150, the oil passes through the depression 143 of thepiston bolt 140, the radial through hole 144, and the radial throughhole 148 of the nut 145, and reaches the first oil chamber 51 (see arrowT3).

Thus, the communication hole 182 of the support-member holding member180, the radial through hole 161 c of the rod holding member 160, theaxial depression 161 a of the rod holding member 160, the inside of therod 150, the depression 143 of the piston bolt 140, the radial throughhole 144, the radial through hole 148 of the nut 145 function as intakepassages through which oil is taken from the reservoir chamber 40 intothe cylinder 230 (first oil chamber 51). The ball 166 and the inclinedsurface 161 e, which is formed on the axial depression 161 a of the rodholding member 160, function as a check valve that allows oil to flowfrom the reservoir chamber 40 into the inside of the rod 150 and thatrestricts discharge of the oil from the inside of the rod 150 to thereservoir chamber 40. The ball 166 and the inclined surface 161 e willbe referred to as “intake-side check valve Vc”.

Flow of Oil in Accordance with Switch State Selected by Front-WheelPassage Switch Unit 300

FIG. 7 illustrates a flow of oil in the front-wheel passage switch unit300 in the first switch state.

When the front-wheel passage switch unit 300 is in the first switchstate at the time of the compression stroke of the front fork 21, oildischarged from the pump 600, which is made up of members such as theattenuation force generation unit 130, the rod 150, and the cylinder230, flows in the upper side direction through the axial communicationholes 394, which are formed in the valve accommodation outer member 390as indicated by arrow P1 in FIG. 7. The oil that has flown in the upperside direction through the axial communication holes 394, which areformed in the valve accommodation outer member 390, flows in the upperside direction through the outer axial communication hole 389 b of thevalve accommodation inner member 380, and then flows in the lower sidedirection through the inner axial communication hole 389 a, which isopen. Then, the oil flows to the reservoir chamber 40 through the firstradial communication holes 397, which are formed in the valveaccommodation outer member 390, and through the discharge passage 41,which is defined between the protrusion 260 b of the base member 260 andthe lower-side end of the support member 400.

Thus, the axial communication holes 394 of the valve accommodation outermember 390, the outer axial communication hole 389 b and the inner axialcommunication hole 389 a of the valve accommodation inner member 380,the first radial communication holes 397 of the valve accommodationouter member 390, and the discharge passage 41 function as a firstcommunication passage R1 (see FIGS. 11A to 11C). Through the firstcommunication passage R1, the cylinder 230 and the reservoir chamber 40communicate with each other. The valve 317, which is mounted on theoperation rod 314, the coil spring 318, and the upper-side end of thevalve accommodation inner member 380 function as a first communicationpassage switch valve V1 (see FIGS. 11A to 11C). The first communicationpassage switch valve V1 opens and closes the first communication passageR1.

FIG. 8 illustrates a flow of oil in the front-wheel passage switch unit300 in the second switch state.

When the front-wheel passage switch unit 300 is in the second switchstate at the time of the compression stroke of the front fork 21, thevalve 317, which is mounted on the operation rod 314, closes the inneraxial communication hole 389 a, which is formed in the valveaccommodation inner member 380. This causes the oil discharged from thepump 600 to flow to the jack chamber 60 as indicated by arrow P2 in FIG.8. Specifically, the oil discharged from the pump 600 pushes up the ball360 against the urging force of the coil spring 361, and flows in theupper side direction through the gap between the outer surface of thevalve accommodation inner member 380 and the inner surface of the valveaccommodation outer member 390 and the gap between the outer surface ofthe accommodation member 370 and the inner surface of the valveaccommodation outer member 390. Then, the oil flows to the outside ofthe valve accommodation outer member 390 through the second radialcommunication holes 398 of the valve accommodation outer member 390. Theoil that has passed through the second radial communication holes 398flows to the jack chamber 60 through the ring-shaped passage 61, whichis defined between the outer surface of the cylinder 230 and the innersurface of the base member 260 of the front-wheel spring lengthadjustment unit 250.

Thus, the gap between the outer surface of the valve accommodation innermember 380 and the inner surface of the valve accommodation outer member390, the gap between the outer surface of the accommodation member 370and the inner surface of the valve accommodation outer member 390, thesecond radial communication holes 398 of the valve accommodation outermember 390, and the ring-shaped passage 61 function as a secondcommunication passage R2 (see FIGS. 11A to 11C). Through the secondcommunication passage R2, the cylinder 230 and the jack chamber 60communicate with each other. The ball 360, the coil spring 361, the disc362, and the ball seat member 365 function as a second communicationpassage switch valve V2 (see FIGS. 11A to 11C). The second communicationpassage switch valve V2 opens and closes the second communicationpassage R2. The second communication passage switch valve V2 alsofunctions as a check valve that allows oil to flow from the inside ofthe cylinder 230 into the jack chamber 60 and that inhibits the oil fromflowing from the jack chamber 60 into the cylinder 230.

FIG. 9 illustrates a flow of oil in the front-wheel passage switch unit300 in the third switch state.

When the front-wheel passage switch unit 300 is in the third switchstate at the time of the compression stroke of the front fork 21, theoil in the jack chamber 60 flows to the reservoir chamber 40 asindicated by arrow P3 in FIG. 9. Specifically, the oil in the jackchamber 60 enters the lower-end depression 382 of the valveaccommodation inner member 380 through the ring-shaped passage 61, whichis defined between the outer surface of the cylinder 230 and the innersurface of the base member 260 of the front-wheel spring lengthadjustment unit 250, through the second radial communication holes 398of the valve accommodation outer member 390, and through the secondradial communication holes 388 of the valve accommodation inner member380. The oil that has entered the lower-end depression 382 of the valveaccommodation inner member 380 flows in the lower side direction throughthe gap between the valve accommodation inner member 380 and the outersurface of the solid cylindrical portion 333 of the valve-body seatmember 330, and enters the lower-end depression 335 of the valve-bodyseat member 330. The oil that has entered the lower-end depression 335of the valve-body seat member 330 flows in the upper side directionthrough the gap between the press member 350 and the valve body 321 andthe gap between the push rod 322 and the valve-body seat member 330, andpasses through the first radial communication holes 387 of the valveaccommodation inner member 380. The oil that has passed through thefirst radial communication holes 387 of the valve accommodation innermember 380 flows to the reservoir chamber 40 through the first radialcommunication holes 397, which are formed in the valve accommodationouter member 390, and through the discharge passage 41, which is definedbetween the protrusion 260 b of the base member 260 and the lower-sideend of the support member 400.

Thus, the ring-shaped passage 61, the second radial communication holes398 of the valve accommodation outer member 390, the second radialcommunication holes 388 of the valve accommodation inner member 380, thegap between the valve accommodation inner member 380 and the outersurface of the solid cylindrical portion 333 of the valve-body seatmember 330, the gap between the press member 350 and the valve body 321,the gap between the push rod 322 and the valve-body seat member 330, thefirst radial communication holes 387 of the valve accommodation innermember 380, the first radial communication holes 397 of the valveaccommodation outer member 390, and the discharge passage 41 function asa third communication passage R3 (see FIGS. 11A to 11C). Through thethird communication passage R3, the jack chamber 60 and the reservoirchamber 40 communicate with each other. The valve body 321 and theinclined surface 335 a of the lower-end depression 335 of the valve-bodyseat member 330 function as a third communication passage switch valveV3 (see FIGS. 11A to 11C). The third communication passage switch valveV3 opens and closes the third communication passage R3.

FIG. 10 illustrates a flow of oil in the front-wheel passage switch unit300 in the fourth switch state.

When the front-wheel passage switch unit 300 is in the fourth switchstate at the time of the compression stroke of the front fork 21, theoil in the jack chamber 60 flows to the reservoir chamber 40 asindicated by arrow P4 in FIG. 10. Specifically, the oil in the jackchamber 60 enters the lower-end depression 382 of the valveaccommodation inner member 380 through the ring-shaped passage 61, thesecond radial communication holes 398 of the valve accommodation outermember 390, and the second radial communication holes 388 of the valveaccommodation inner member 380. The oil that has entered the lower-enddepression 382 of the valve accommodation inner member 380 flows in theupper side direction through the gap defined by the inclined surface 331of the conical portion 332 of the valve-body seat member 330, the O ring337, and the inclined surface on the conical depression 382 c of thevalve accommodation inner member 380, and passes through the firstradial communication holes 387 of the valve accommodation inner member380. The oil that has passed the first radial communication holes 387 ofthe valve accommodation inner member 380 flows to the reservoir chamber40 through the first radial communication holes 397, which are formed inthe valve accommodation outer member 390, and through the dischargepassage 41, which is defined between the protrusion 260 b of the basemember 260 and the lower-side end of the support member 400.

Thus, the ring-shaped passage 61, the second radial communication holes398 of the valve accommodation outer member 390, the second radialcommunication holes 388 of the valve accommodation inner member 380, thegap defined by the inclined surface 331 of the valve-body seat member330, the O ring 337, and the inclined surface on the conical depression382 c of the valve accommodation inner member 380, the first radialcommunication holes 387 of the valve accommodation inner member 380, thefirst radial communication holes 397 of the valve accommodation outermember 390, and the discharge passage 41 function as a fourthcommunication passage R4 (not illustrated). Through the fourthcommunication passage R4, the jack chamber 60 and the reservoir chamber40 communicate with each other. The inclined surface 331 of the conicalportion 332 of the valve-body seat member 330, the O ring 337, and theinclined surface on the conical depression 382 c of the valveaccommodation inner member 380 function as a fourth communicationpassage switch valve V4 (not illustrated). The fourth communicationpassage switch valve V4 opens and closes the fourth communicationpassage R4.

Change from Third Switch State to Fourth Switch State of Front-WheelPassage Switch Unit 300

When the front-wheel passage switch unit 300 is in the third switchstate, the oil in the jack chamber 60 flows to the reservoir chamber 40as indicated by arrow P3 illustrated in FIG. 9. This flow of the oilcauses the amount of the oil in the jack chamber 60 to decrease, causinga reduction in length of the front-wheel spring 500. The reduction inlength of the spring 500 causes the pressure in the jack chamber 60 todecrease. As a result, the pressure in a back pressure chamber definedbetween the valve-body seat member 330 and the accommodation member 370at the time when the front-wheel passage switch unit 300 is in the thirdswitch state is lower than the pressure in the back pressure chamber atthe time when the front-wheel passage switch unit 300 is in the secondswitch state. This causes the valve-body seat member 330 to start tomove in the lower side direction.

When the coil 311 of the front-wheel solenoid 310 is supplied a currentthat is equal to or higher than the third reference current, the pushrod 322 moves the valve body 321 further in the lower side directionthan when the passage switch unit 300 is in the third switch state. Thisenlarges the gap between the valve body 321 and the inclined surface 335a of the lower-end depression 335 of the valve-body seat member 330. Asa result, the pressure in the jack chamber 60 further decreases, causinga further decrease in the pressure in the back pressure chamber. Thefurther decrease in the pressure in the back pressure chamber causes thevalve-body seat member 330 to move in the lower side direction. Thiscauses the inclined surface 331 of the conical portion 332 of thevalve-body seat member 330 to move away from the inclined surface on theconical depression 382 c of the valve accommodation inner member 380.Thus, the third switch state changes to the fourth switch state.

Communication Passages Open or Closed in Accordance with Switch StateSelected by Front-Wheel Passage Switch Unit 300

FIG. 11A illustrates whether the first communication passage R1, thesecond communication passage R2, and the third communication passage R3are open or closed when the front-wheel passage switch unit 300 is inthe first switch state. FIG. 11B illustrates whether the firstcommunication passage R1, the second communication passage R2, and thethird communication passage R3 are open or closed when the front-wheelpassage switch unit 300 is in the second switch state. FIG. 11Cillustrates whether the first communication passage R1, the secondcommunication passage R2, and the third communication passage R3 areopen or closed when the front-wheel passage switch unit 300 is in thethird switch state.

As illustrated in FIG. 11A, when the current supplied to the coil 311 ofthe front-wheel solenoid 310 is less than the first reference current,the front-wheel passage switch unit 300 is in the first switch state.That is, the first communication passage switch valve V1 is open and thethird communication passage switch valve V3 is closed. This causes theoil discharged from the pump 600 to reach the reservoir chamber 40through the first communication passage R1. In this case, the oildischarged from the pump 600 does not have such a high pressure as toopen the second communication passage switch valve V2. Hence, the oildoes not flow through the second communication passage R2. In otherwords, since the first communication passage switch valve V1 is open,the second communication passage switch valve V2 is closed. In the firstswitch state, the oil in the jack chamber 60 does not increase ordecrease.

As illustrated in FIG. 11B, when the current supplied to the coil 311 ofthe front-wheel solenoid 310 is equal to or higher than the firstreference current and less than the second reference current, thefront-wheel passage switch unit 300 is in the second switch state. Thatis, the first communication passage switch valve V1 and the thirdcommunication passage switch valve V3 are closed. Thus, the oildischarged from the pump 600 opens the second communication passageswitch valve V2 to reach the jack chamber 60 through the secondcommunication passage R2. In the second switch state, the amount of theoil in the jack chamber 60 increases.

As illustrated in FIG. 11C, when the current supplied to the coil 311 ofthe front-wheel solenoid 310 is equal to or higher than the secondreference current and less than the third reference current, thefront-wheel passage switch unit 300 is in the third switch state. Thatis, the first communication passage switch valve V1 is closed and thethird communication passage switch valve V3 is open. This causes the oilin the jack chamber 60 to reach the reservoir chamber 40 through thethird communication passage R3. In the third switch state, the amount ofthe oil in the jack chamber 60 decreases.

When the current supplied to the coil 311 of the front-wheel solenoid310 is equal to or higher than the third reference current, thefront-wheel passage switch unit 300 is in the fourth switch state. Thatis, the first communication passage switch valve V1 is closed and thefourth communication passage switch valve V4 is open. This causes theoil in the jack chamber 60 to reach the reservoir chamber 40 through thefourth communication passage R4.

The passage defined in the fourth switch state by the gap defined by theinclined surface 331 of the conical portion 332 of the valve-body seatmember 330, the O ring 337, and the inclined surface on the valveaccommodation inner member 380 is wider than the passage defined in thethird switch state by the gap between the valve accommodation innermember 380 and the outer surface of the solid cylindrical portion 333 ofthe valve-body seat member 330.

The passage defined in the third switch state by the gap between thevalve body 321 and the inclined surface 335 a on the valve-body seatmember 330 is narrower than the passage defined in the third switchstate by the gap between the valve accommodation inner member 380 andthe outer surface of the solid cylindrical portion 333 of the valve-bodyseat member 330. Therefore, when the passage switch unit 300 is in thefourth switch state, the amount of the oil in the jack chamber 60decreases more quickly than when the passage switch unit 300 is in thethird switch state.

Up-and-Down of Vehicle Height

In the front fork 21 operating in the above-described manner, when thefront-wheel passage switch unit 300 is in the second switch state, theoil discharged from the pump 600 at the time of the compression strokeflows into the jack chamber 60, increasing the amount of oil in the jackchamber 60. The increase in the amount of oil in the jack chamber 60causes the upper-side end support member 270 to move in the lower-sidedirection relative to the base member 260 of the front-wheel springlength adjustment unit 250. The movement of the upper-side end supportmember 270 in the lower-side direction relative to the base member 260causes the spring length of the front-wheel spring 500 to shorten. Theshortened spring length of the front-wheel spring 500 causes the springforce of the front-wheel spring 500 in pressing the upper-side endsupport member 270 to increase as compared with the spring force beforethe movement of the upper-side end support member 270 relative to thebase member 260. This causes an increase in preset load (pre-load),which is an amount of load that keeps the position of the body frame 11unchanged relative to the position of the front wheel 2 even when forceacts from the body frame 11 toward the front wheel 2 side. In this case,the amount of depression of the front fork 21 is smaller when the sameamount of force acts in the axial direction from the body frame 11 (seat19) side. Thus, when the spring length of the front-wheel spring 500 isshortened due to the movement of the upper-side end support member 270relative to the base member 260, the height of the seat 19 increases ascompared with the height of the seat 19 before the movement of theupper-side end support member 270 relative to the base member 260 (thatis, the vehicle height increases).

When the front-wheel passage switch unit 300 is in the third switchstate or the fourth switch state, the amount of oil in the jack chamber60 decreases. The decrease in the amount of oil causes the upper-sideend support member 270 to move in the upper-side direction relative tothe base member 260 of the front-wheel spring length adjustment unit250. The movement of the upper-side end support member 270 in theupper-side direction relative to the base member 260 causes the springlength of the front-wheel spring 500 to increase. The increased springlength of the front-wheel spring 500 causes the spring force of thefront-wheel spring 500 in pressing the upper-side end support member 270to reduce as compared with the spring force before the movement of theupper-side end support member 270 relative to the base member 260. Thiscauses the preset load (pre-load) to decrease, and the amount ofdepression of the front fork 21 is larger when the same amount of forceacts in the axial direction from the body frame 11 (seat 19) side. Thus,when the spring length of the front-wheel spring 500 is increased due tothe movement of the upper-side end support member 270 in the upper-sidedirection relative to the base member 260, the height of the seat 19decreases as compared with the height of the seat 19 before the movementof the upper-side end support member 270 relative to the base member 260(that is, the vehicle height decreases). When the front-wheel passageswitch unit 300 is in the fourth switch state, the amount of the oil inthe jack chamber 60 decreases more quickly than when the front-wheelpassage switch unit 300 is in the third switch state, as describedabove. Hence, when the front-wheel passage switch unit 300 is in thefourth switch state, the vehicle height decreases more quickly than whenthe front-wheel passage switch unit 300 is in the third switch state.

When the front-wheel passage switch unit 300 is in the first switchstate, the oil discharged from the pump 600 at the time of thecompression stroke flows into the reservoir chamber 40, and thus theamount of oil in the jack chamber 60 does not increase or decrease.Thus, the height of the seat 19 is maintained (that is, the vehicleheight is maintained).

Configuration of Rear Suspension 22

The rear suspension 22 is disposed between the body 10 and the rearwheel 3 of the motorcycle 1, and supports the rear wheel 3. The rearsuspension 22 includes an axle side unit, a body side unit, and arear-wheel spring 502 (see FIG. 1). The axle side unit is mounted on theaxle of the rear wheel 3. The body side unit is mounted on the body 10.The rear-wheel spring 502 is disposed between the axle side unit and thebody side unit, and absorbs vibrations transmitted to the rear wheel 3caused by the roughness of the ground surface. The rear-wheel spring 502has an upper-side end supported on the body side unit and has alower-side end supported on the axle side unit.

The axle side unit includes an attenuation force generation unit, a rod152 (see FIG. 1), and a spring lower-side end support member 153 (seeFIG. 1). The attenuation force generation unit generates attenuationforce utilizing viscous resistance of oil. The rod 152 holds theattenuation force generation unit. The spring lower-side end supportmember 153 supports the lower-side end of the rear-wheel spring 502.

The body side unit includes a cylinder 232 (see FIG. 1), a rear-wheelspring length adjustment unit 252 (see FIG. 1), and a rear-wheel passageswitch unit 302 (see FIG. 1). The attenuation force generation unit isinserted in the cylinder 232. The rear-wheel spring length adjustmentunit 252 is an example of the adjustor that supports the upper-side endof the rear-wheel spring 502 to adjust (change) the length of therear-wheel spring 502. The rear-wheel passage switch unit 302 is mountedoutside of the cylinder 232 to switch among passages of oil.

The rear suspension 22 also includes a reservoir chamber (which is thestorage chamber) and a pump. The reservoir chamber stores the oil. Thepump includes the cylinder 232. When the relative distance between thebody 10 and the rear wheel 3 increases, the pump takes into the cylinder232 the oil stored in the reservoir chamber. When the relative distancebetween the body 10 and the rear wheel 3 decreases, the pump dischargesthe oil out of the cylinder 232.

Similarly to the front-wheel spring length adjustment unit 250 of thefront fork 21, the rear-wheel spring length adjustment unit 252 includesa base member 253 and an upper-side end support member 254. The basemember 253 is secured to a side of the body frame 11. The upper-side endsupport member 254 supports the upper-side end of the rear-wheel spring502 and moves in the axial direction relative to the base member 253 soas to change the length of the rear-wheel spring 502. The rear-wheelspring length adjustment unit 252 includes a jack chamber (which is theaccommodation chamber) that accommodates oil. The upper-side end supportmember 254 supports the upper-side end of the rear-wheel spring 502. Therear-wheel spring length adjustment unit 252 adjusts the length of therear-wheel spring 502 in accordance with the amount of oil in the jackchamber.

The rear suspension 22 also includes a rear-wheel relative positiondetector 282 (which is the relative position detector) (see FIG. 12) todetect the position, relative to the body frame 11, of the member tosupport the upper-side end of the rear-wheel spring 502. In anon-limiting embodiment, the rear-wheel relative position detector 282detects the amount of displacement of the upper-side end support member254 in the axial direction relative to the base member 253, that is, theamount of displacement of the upper-side end support member 254 in theaxial direction relative to the body frame 11. In a non-limitingembodiment, a coil is wound around the outer surface of the base member253, and the upper-side end support member 254 is made of a magneticmaterial. Based on the impedance of the coil, which changes inaccordance with displacement of the upper-side end support member 254 inthe vertical direction relative to the base member 253, the rear-wheelrelative position detector 282 detects the amount of displacement of theupper-side end support member 254.

Communication Passages Open or Closed in Accordance with Switch StateSelected by Rear-Wheel Passage Switch Unit 302

The rear-wheel passage switch unit 302 has a configuration and functionssimilar to the configuration and functions of the front-wheel passageswitch unit 300 of the front fork 21. Specifically, the rear-wheelpassage switch unit 302 includes a first communication passage R1, asecond communication passage R2, and a third communication passage R3.The first communication passage R1 allows the inside of the cylinder 232and the reservoir chamber to communicate with each other. The secondcommunication passage R2 allows the inside of the cylinder 232 and thejack chamber to communicate with each other. The third communicationpassage R3 allows the jack chamber and the reservoir chamber tocommunicate with each other. The rear-wheel passage switch unit 302 alsoincludes a first communication passage switch valve V1, a secondcommunication passage switch valve V2, and a third communication passageswitch valve V3. The first communication passage switch valve V1 opensand closes the first communication passage R1. The second communicationpassage switch valve V2 opens and closes the second communicationpassage R2. The third communication passage switch valve V3 opens andcloses the third communication passage R3.

When the current supplied to the rear-wheel passage switch unit 302 isless than a predetermined first reference current, the rear-wheelpassage switch unit 302 opens the first communication passage R1 andcloses the third communication passage R3. When the current supplied tothe rear-wheel passage switch unit 302 is equal to or higher than thefirst reference current and less than a second reference current, therear-wheel passage switch unit 302 closes the first communicationpassage R1 and the third communication passage R3. When the currentsupplied to the rear-wheel passage switch unit 302 is equal to or higherthan the second reference current, the rear-wheel passage switch unit302 opens the third communication passage R3 and closes the firstcommunication passage R1.

Specifically, when the current supplied to the rear-wheel passage switchunit 302 is less than the predetermined first reference current, therear-wheel passage switch unit 302 allows the inside of the cylinder 232and the reservoir chamber to communicate with each other to guide theoil discharged from the pump into the reservoir chamber. When thecurrent supplied to the rear-wheel passage switch unit 302 is equal toor higher than the first reference current and less than the secondreference current, the rear-wheel passage switch unit 302 allows theinside of the cylinder 232 and the jack chamber to communicate with eachother to guide the oil discharged from the pump into the jack chamber.When the current supplied to the rear-wheel passage switch unit 302 isequal to or higher than the second reference current, the rear-wheelpassage switch unit 302 allows the jack chamber and the reservoirchamber to communicate with each other to guide the oil accommodated inthe jack chamber into the reservoir chamber.

More specifically, when the current supplied to a coil of a rear-wheelsolenoid of the rear-wheel passage switch unit 302 is less than thefirst reference current, the rear-wheel passage switch unit 302 is in afirst switch state, in which the first communication passage switchvalve V1 is open and the third communication passage switch valve V3 isclosed. This causes the oil discharged from the pump to reach thereservoir chamber through the first communication passage R1. In thiscase, since the oil discharged from the pump does not have such a highpressure as to open the second communication passage switch valve V2,the oil does not flow through the second communication passage R2. Inother words, since the first communication passage switch valve V1 isopen, the second communication passage switch valve V2 is closed. In thefirst switch state, the oil in the jack chamber does not increase nordecrease, and consequently, the vehicle height remains unchanged.

When the current supplied to the coil of the rear-wheel solenoid of therear-wheel passage switch unit 302 is equal to or higher than the firstreference current and less than the second reference current, therear-wheel passage switch unit 302 is in a second switch state, in whichthe first communication passage switch valve V1 and the thirdcommunication passage switch valve V3 are closed. This causes the oildischarged from the pump to open the second communication passage switchvalve V2 and reach the jack chamber. In the second switch state, theamount of oil in the jack chamber increases to increase the vehicleheight.

When the current supplied to the coil of the rear-wheel solenoid of therear-wheel passage switch unit 302 is equal to or higher than the secondreference current and less than the third reference current, therear-wheel passage switch unit 302 is in a third switch state, in whichthe first communication passage switch valve V1 is closed and the thirdcommunication passage switch valve V3 is open. This causes the oil inthe jack chamber to reach the reservoir chamber through the thirdcommunication passage R3. In the third switch state, the amount of oilin the jack chamber decreases to decrease the vehicle height.

When the current supplied to the coil of the rear-wheel solenoid of therear-wheel passage switch unit 302 is equal to or higher than the thirdreference current, the rear-wheel passage switch unit 302 is in a fourthswitch state, in which the first communication passage switch valve V1is closed and the fourth communication passage switch valve V4 is open.This causes the oil in the jack chamber to reach the reservoir chamberthrough the fourth communication passage R4. In the fourth switch state,the amount of oil in the jack chamber decreases more quickly to decreasethe vehicle height more quickly than in the third switch state.

Configuration of Controller 70

The controller 70 will be described below.

FIG. 12 is a block diagram of the controller 70.

The controller 70 includes a CPU, a ROM, and a RAM. The ROM storesprograms to be executed in the CPU and various kinds of data. The RAM isused as, for example, an operation memory for the CPU. The controller 70receives inputs such as signals output from the front-wheel rotationdetection sensor 31, the rear-wheel rotation detection sensor 32, thefront-wheel relative position detector 281, and the rear-wheel relativeposition detector 282.

The controller 70 includes a front-wheel rotation speed calculator 71and a rear-wheel rotation speed calculator 72. The front-wheel rotationspeed calculator 71 calculates the rotation speed of the front wheel 2based on an output signal from the front-wheel rotation detection sensor31. The rear-wheel rotation speed calculator 72 calculates the rotationspeed of the rear wheel 3 based on an output signal from the rear-wheelrotation detection sensor 32. The front-wheel rotation speed calculator71 and the rear-wheel rotation speed calculator 72 each obtain arotation angle based on a pulse signal, which is the output signal fromthe sensor, and differentiate the rotation angle by time elapsed so asto calculate the rotation speed.

The controller 70 includes a front-wheel displacement amount obtainer73. The front-wheel displacement amount obtainer 73 obtains afront-wheel displacement amount Lf based on the output signal from thefront-wheel relative position detector 281. The front-wheel displacementamount Lf is the amount of displacement of the upper-side end supportmember 270 of the front-wheel spring length adjustment unit 250 relativeto the base member 260. The controller 70 also includes a rear-wheeldisplacement amount obtainer 74. The rear-wheel displacement amountobtainer 74 obtains a rear-wheel displacement amount Lr based on theoutput signal from the rear-wheel relative position detector 282. Therear-wheel displacement amount Lr is the amount of displacement of theupper-side end support member 254 of the rear-wheel spring lengthadjustment unit 252 relative to the base member 253. The front-wheeldisplacement amount obtainer 73 obtains the front-wheel displacementamount Lf based on a correlation between the impedance of the coil andthe front-wheel displacement amount Lf. The rear-wheel displacementamount obtainer 74 obtains the rear-wheel displacement amount Lr basedon a correlation between the impedance of the coil and the rear-wheeldisplacement amount Lr. The correlations are stored in the ROM inadvance.

The controller 70 also includes a vehicle speed obtainer 76 to obtain avehicle speed Vv, which is a traveling speed of the motorcycle 1, basedon the rotation speed of the front wheel 2 calculated by the front-wheelrotation speed calculator 71 and/or based on the rotation speed of therear wheel 3 calculated by the rear-wheel rotation speed calculator 72.The vehicle speed obtainer 76 uses the front-wheel rotation speed Rf orthe rear-wheel rotation speed Rr to calculate the traveling speed of thefront wheel 2 or the rear wheel 3 so as to obtain the vehicle speed Vv.The traveling speed of the front wheel 2 is calculated using thefront-wheel rotation speed Rf and the outer diameter of the tire of thefront wheel 2. The moving speed of the rear wheel 3 is calculated usingthe rear-wheel rotation speed Rr and the outer diameter of the tire ofthe rear wheel 3. When the motorcycle 1 is traveling in a normal state,it can be construed that the vehicle speed Vv is equal to the travelingspeed of the front wheel 2 and/or the traveling speed of the rear wheel3. Alternatively, the vehicle speed obtainer 76 may use an average valueof the front-wheel rotation speed Rf and the rear-wheel rotation speedRr to calculate an average traveling speed of the front wheel 2 and therear wheel 3 so as to obtain the vehicle speed Vv.

The controller 70 also includes a passage switch unit controller 77 tocontrol the switch states of the front-wheel passage switch unit 300 andthe switch states of the rear-wheel passage switch unit 302 based on thevehicle speed Vv obtained by the vehicle speed obtainer 76. The passageswitch unit controller 77 will be detailed later.

The front-wheel rotation speed calculator 71, the rear-wheel rotationspeed calculator 72, the front-wheel displacement amount obtainer 73,the rear-wheel displacement amount obtainer 74, the vehicle speedobtainer 76, and the passage switch unit controller 77 are implementedby the CPU executing software stored in storage areas of, for example,the ROM.

The passage switch unit controller 77 of the controller 70 will now bedescribed in detail.

FIG. 13 is a block diagram of the passage switch unit controller 77.

The passage switch unit controller 77 includes a target displacementamount determiner 770. The target displacement amount determiner 770includes a front-wheel target displacement amount determiner 771 and arear-wheel target displacement amount determiner 772. The front-wheeltarget displacement amount determiner 771 determines a front-wheeltarget displacement amount, which is a target value of the front-wheeldisplacement amount Lf. The rear-wheel target displacement amountdeterminer 772 determines a rear-wheel target displacement amount, whichis a target value of the rear-wheel displacement amount Lr. The passageswitch unit controller 77 also includes a target current determiner 710and a control section 720. The target current determiner 710 determinesa target current to be supplied to the front-wheel solenoid 310 of thefront-wheel passage switch unit 300 and the rear-wheel solenoid (notillustrated) of the rear-wheel passage switch unit 302. The controlsection 720 performs control such as feedback control based on thetarget current determined by the target current determiner 710. Thepassage switch unit controller 77 further includes a malfunctiondetector 780. The malfunction detector 780 detects a malfunction (suchas a decreasing malfunction, described later) of the current (actualcurrent) actually flowing to the front-wheel solenoid 310 and therear-wheel solenoid being higher than the target current.

The passage switch unit controller 77 includes a front-wheel relay 791and a rear-wheel relay 792. The front-wheel relay 791 is connected to acurrent path between a front-wheel solenoid driver 733, described later,and the front-wheel solenoid 310 so as to pass and shut off the currentsupplied from the front-wheel solenoid driver 733 to the front-wheelsolenoid 310. The rear-wheel relay 792 is connected to a current pathbetween a rear-wheel solenoid driver 743 and the rear-wheel solenoid soas to pass and shut off the current supplied from the rear-wheelsolenoid driver 743 to the rear-wheel solenoid. The front-wheel solenoiddriver 733 and the rear-wheel solenoid driver 743 are non-limitingexamples of an actuator driver. The passage switch unit controller 77also includes a relay driver 790 to control the front-wheel relay 791and the rear-wheel relay 792 to operate.

The target displacement amount determiner 770 determines a targetdisplacement amount based on the vehicle speed Vv obtained by thevehicle speed obtainer 76 and based on which control position a vehicleheight adjustment switch (not illustrated) of the motorcycle 1 occupies.The vehicle height adjustment switch is what is called a dial switch.The rider of the motorcycle 1 turns the dial of the switch to selectbetween “Low”, “Medium”, and “High”. The vehicle height adjustmentswitch is disposed in the vicinity of the speedometer, for example.

After the motorcycle 1 starts traveling, when the vehicle speed Vvobtained by the vehicle speed obtainer 76 is lower than a predeterminedupward vehicle speed Vu, the target displacement amount determiner 770determines the target displacement amount as zero. When the vehiclespeed Vv changes from the value lower than the upward vehicle speed Vuto a value equal to or higher than the upward vehicle speed Vu, thetarget displacement amount determiner 770 determines the targetdisplacement amount at a predetermined value in accordance with thecontrol position of the vehicle height adjustment switch. Morespecifically, when the vehicle speed Vv changes from the value lowerthan the upward vehicle speed Vu to a value equal to or higher than theupward vehicle speed Vu, the front-wheel target displacement amountdeterminer 771 determines the front-wheel target displacement amount asa predetermined front-wheel target displacement amount Lf0 in accordancewith the control position of the vehicle height adjustment switch. Whenthe vehicle speed Vv changes from the value lower than the upwardvehicle speed Vu to a value equal to or higher than the upward vehiclespeed Vu, the rear-wheel target displacement amount determiner 772determines the rear-wheel target displacement amount as a predeterminedrear-wheel target displacement amount Lr0 in accordance with the controlposition of the vehicle height adjustment switch. Then, while thevehicle speed Vv obtained by the vehicle speed obtainer 76 is equal toor higher than the upward vehicle speed Vu, the front-wheel targetdisplacement amount determiner 771 determines the front-wheel targetdisplacement amount as the predetermined front-wheel target displacementamount Lf0, and the rear-wheel target displacement amount determiner 772determines the rear-wheel target displacement amount as thepredetermined rear-wheel target displacement amount Lr0. The ROM stores,in advance, relationships of the control positions of the vehicle heightadjustment switch, the predetermined front-wheel target displacementamount Lf0 that accords with the control position, and the predeterminedrear-wheel target displacement amount Lr0 that accords with the controlposition. The vehicle height of the motorcycle 1 is determined inaccordance with the front-wheel displacement amount Lf and therear-wheel displacement amount Lr. In a non-limiting embodiment, atarget vehicle height, which is a target value of the vehicle height ofthe motorcycle 1, is determined in accordance with the control positionof the vehicle height adjustment switch. The predetermined front-wheeltarget displacement amount Lf0 and the predetermined rear-wheel targetdisplacement amount Lr0 in accordance with the target vehicle height aredetermined in advance and stored in the ROM.

When the vehicle speed Vv of the motorcycle 1 changes from the valueequal to or higher than the upward vehicle speed Vu to a value equal toor lower than a predetermined downward vehicle speed Vd, the targetdisplacement amount determiner 770 determines the target displacementamount as zero. That is, the front-wheel target displacement amountdeterminer 771 and the rear-wheel target displacement amount determiner772 respectively determine the front-wheel target displacement amountand the rear-wheel target displacement amount as zero. In a non-limitingexample, the upward vehicle speed Vu is 10 km/h, and the downwardvehicle speed Vd is 8 km/h.

The target current determiner 710 includes a front-wheel target currentdeterminer 711 and a rear-wheel target current determiner 712. Based onthe front-wheel target displacement amount determined by the front-wheeltarget displacement amount determiner 771, the front-wheel targetcurrent determiner 711 determines a front-wheel target current, which isa target current of the front-wheel solenoid 310 of the front-wheelpassage switch unit 300. Based on the rear-wheel target displacementamount determined by the rear-wheel target displacement amountdeterminer 772, the rear-wheel target current determiner 712 determinesa rear-wheel target current, which is a target current of the rear-wheelsolenoid of the rear-wheel passage switch unit 302.

In a non-limiting embodiment, a map indicating correspondence betweenthe front-wheel target displacement amount and the front-wheel targetcurrent is prepared based on empirical rules and stored in the ROM inadvance. The front-wheel target current determiner 711 substitutes thefront-wheel target displacement amount determined by the front-wheeltarget displacement amount determiner 771 into the map to determine thefront-wheel target current.

In a non-limiting embodiment, a map indicating correspondence betweenthe rear-wheel target displacement amount and the rear-wheel targetcurrent is prepared based on empirical rules and stored in the ROM inadvance. The rear-wheel target current determiner 712 substitutes therear-wheel target displacement amount determined by the rear-wheeltarget displacement amount determiner 772 into the map to determine therear-wheel target current.

In the determination of the front-wheel target current based on thefront-wheel target displacement amount determined by the front-wheeltarget displacement amount determiner 771, the front-wheel targetcurrent determiner 711 may perform feedback control based on an errorbetween the front-wheel target displacement amount determined by thefront-wheel target displacement amount determiner 771 and thefront-wheel displacement amount Lf obtained by the front-wheeldisplacement amount obtainer 73 so as to determine the front-wheeltarget current. Similarly, in the determination of the rear-wheel targetcurrent based on the rear-wheel target displacement amount determined bythe rear-wheel target displacement amount determiner 772, the rear-wheeltarget current determiner 712 may perform feedback control based on anerror between the rear-wheel target displacement amount determined bythe rear-wheel target displacement amount determiner 772 and therear-wheel displacement amount Lr obtained by the rear-wheeldisplacement amount obtainer 74 so as to determine the rear-wheel targetcurrent.

The control section 720 includes a front-wheel solenoid driver 733, afront-wheel operation controller 730, and a front-wheel current detector734. The front-wheel solenoid driver 733 drives the front-wheel solenoid310 of the front-wheel passage switch unit 300. The front-wheeloperation controller 730 controls the operation of the front-wheelsolenoid driver 733. The front-wheel current detector 734 detects thecurrent flowing to the front-wheel solenoid 310. The control section 720also includes a rear-wheel solenoid driver 743, a rear-wheel operationcontroller 740, and a rear-wheel current detector 744. The rear-wheelsolenoid driver 743 drives the rear-wheel solenoid. The rear-wheeloperation controller 740 controls the operation of the rear-wheelsolenoid driver 743. The rear-wheel current detector 744 detects thecurrent flowing to the rear-wheel solenoid.

The front-wheel operation controller 730 includes a front-wheel feedback(F/B) controller 731 and a front-wheel PWM controller 732. Thefront-wheel feedback controller 731 performs feedback control based onan error between the front-wheel target current determined by thefront-wheel target current determiner 711 and a current detected by thefront-wheel current detector 734 (front-wheel detection current). Thefront-wheel feedback controller 731 is a non-limiting example of atarget current setter. The front-wheel PWM controller 732 performs PWMcontrol of the front-wheel solenoid 310.

The rear-wheel operation controller 740 includes a rear-wheel feedback(F/B) controller 741 and a rear-wheel PWM controller 742. The rear-wheelfeedback controller 741 performs feedback control based on an errorbetween the rear-wheel target current determined by the rear-wheeltarget current determiner 712 and a current detected by the rear-wheelcurrent detector 744 (rear-wheel detection current). The rear-wheelfeedback controller 741 is also a non-limiting example of the targetcurrent setter. The rear-wheel PWM controller 742 performs PWM controlof the rear-wheel solenoid.

The front-wheel feedback controller 731 calculates an error between thefront-wheel target current and the front-wheel detection currentdetected by the front-wheel current detector 734, and performs feedbackprocessing to make the error zero. The rear-wheel feedback controller741 calculates an error between the rear-wheel target current and therear-wheel detection current detected by the rear-wheel current detector744, and performs feedback processing to make the error zero. In anon-limiting embodiment, the front-wheel feedback controller 731subjects the error between the front-wheel target current and thefront-wheel detection current to proportional processing using aproportional element and to integral processing using an integralelement, and adds these values together using an adder. The rear-wheelfeedback controller 741 subjects the error between the rear-wheel targetcurrent and the rear-wheel detection current to proportional processingusing a proportional element and to integral processing using anintegral element, and adds these values together using an adder. Inanother non-limiting embodiment, the front-wheel feedback controller 731subjects the error between the target current and the detection currentto proportional processing using a proportional element, to integralprocessing using an integral element, and to differential processingusing a differential element, and adds these values together using anadder. The rear-wheel feedback controller 741 subjects the error betweenthe target current and the detection current to proportional processingusing a proportional element, to integral processing using an integralelement, and to differential processing using a differential element,and adds these values together using an adder.

The front-wheel PWM controller 732 changes the duty ratio (=t/T×100(%))of the pulse width (t) in a predetermined cycle (T), and performs PWMcontrol of the opening (voltage applied to the coil 311 of thefront-wheel solenoid 310) of the front-wheel solenoid 310. When the PWMcontrol is performed, the voltage is applied to the coil 311 of thefront-wheel solenoid 310 in the form of a pulse that accords with theduty ratio. Here, due to the impedance of the coil 311, the currentflowing to the coil 311 of the front-wheel solenoid 310 cannot change tofollow the voltage applied in the form of a pulse but is output in aweakened form, and the current flowing in the coil 311 of thefront-wheel solenoid 310 is increased and decreased in proportion to theduty ratio. In a non-limiting embodiment, when the front-wheel targetcurrent is zero, the front-wheel PWM controller 732 sets the duty ratioat zero. When the front-wheel target current is at its maximum, thefront-wheel PWM controller 732 sets the duty ratio at 100%.

Similarly, the rear-wheel PWM controller 742 changes the duty ratio andperforms PWM control of the opening (voltage applied to the coil of therear-wheel solenoid) of the rear-wheel solenoid. When the PWM control isperformed, the voltage is applied to the coil of the rear-wheel solenoidin the form of a pulse that accords with the duty ratio, and the currentflowing in the coil of the rear-wheel solenoid is increased anddecreased in proportion to the duty ratio. In a non-limiting embodiment,when the rear-wheel target current is zero, the rear-wheel PWMcontroller 742 sets the duty ratio at zero. When the rear-wheel targetcurrent is at its maximum, the rear-wheel PWM controller 742 sets theduty ratio at 100%.

The front-wheel solenoid driver 733 includes, for example, a transistor(FET). The transistor is a switching element connected between thepositive electrode line of the power source and the coil 311 of thefront-wheel solenoid 310. The front-wheel solenoid driver 733 drives thegate of the transistor to switch the transistor so as to control driveof the front-wheel solenoid 310. The rear-wheel solenoid driver 743includes, for example, a transistor connected between the positiveelectrode line of the power source and the coil of the rear-wheelsolenoid. The rear-wheel solenoid driver 743 drives the gate of thetransistor to switch the transistor so as to control drive of therear-wheel solenoid.

From voltage across the terminals of a shunt resistor connected to thefront-wheel solenoid driver 733, the front-wheel current detector 734detects the value of the current flowing to the front-wheel solenoid310. From voltage across the terminals of a shunt resistor connected tothe rear-wheel solenoid driver 743, the rear-wheel current detector 744detects the value of the current flowing to the rear-wheel solenoid.

The malfunction detector 780 will be detailed later.

The relay driver 790 changes the front-wheel relay 791 and therear-wheel relay 792 from OFF (open state) to ON (closed state) to passthe current and from ON to OFF to shut off the current.

In the motorcycle 1 of the above-described configuration, the passageswitch unit controller 77 of the controller 70 determines the targetcurrent based on the target vehicle height in accordance with thecontrol position of the vehicle height adjustment switch, and performsPWM control to cause an actual current supplied to the front-wheelsolenoid 310 and the rear-wheel solenoid to be the target currentdetermined. That is, the front-wheel PWM controller 732 and therear-wheel PWM controller 742 of the passage switch unit controller 77change the duty ratios to control power supplied to the coil 311 of thefront-wheel solenoid 310 and the coil of the rear-wheel solenoid so asto control the front-wheel solenoid 310 and the rear-wheel solenoid intodesired openings.

When there occurs a malfunction of the current (actual current) actuallyflowing to the front-wheel solenoid 310 and the rear-wheel solenoidbeing higher than the target current, the controller 70 of theabove-described configuration cannot control the current supplied to thefront-wheel solenoid 310 and the rear-wheel solenoid. This hindersappropriate adjustment of the vehicle height. In particular,irrespective of the target current being an increasing current forincreasing the vehicle height (equal to or higher than the firstreference current and less than the second reference current) or amaintaining current for maintaining the vehicle height (equal to orhigher than zero and less than the first reference current), there mayoccur such a decreasing malfunction that a current equal to or higherthan the second reference current, which decreases the vehicle height,flows to the front-wheel solenoid 310 and the rear-wheel solenoid. Inthis case, the vehicle height may suddenly decrease during travel. It isnoted that the increasing current is, in other words, an increasingcurrent for increasing the front-wheel displacement amount Lf and therear-wheel displacement amount Lr. The maintaining current is, in otherwords, a maintaining current for maintaining the front-wheeldisplacement amount Lf and the rear-wheel displacement amount Lr.

As a malfunction (such as the decreasing malfunction) of the actualcurrent of the front-wheel solenoid 310 and the rear-wheel solenoidbeing higher than the target current, there may be considered, forexample, a malfunction of the transistor (FET) of the front-wheelsolenoid driver 733 and the rear-wheel solenoid driver 743 and amalfunction of the coil of the front-wheel solenoid 310 and therear-wheel solenoid.

FIG. 14A is a time chart illustrating a disadvantageous state when thereoccurs a malfunction of the actual current of the front-wheel solenoid310 being higher than the target current. For example, in order tomaintain the vehicle height after increasing the vehicle height, thetarget current is set at a value equal to or higher than zero and lessthan the first reference current. The current supplied to thefront-wheel solenoid 310 is controlled to be the set target current. Inthis case, there may occur a malfunction of the actual current of thefront-wheel solenoid 310 (front-wheel actual current) being higher thanthe target current. In order to increase the vehicle height, the targetcurrent is set at a value equal to or higher than the first referencecurrent and less than the second reference current. The current suppliedto the front-wheel solenoid 310 is controlled to be the set targetcurrent. In this case, the same malfunction may occur. Irrespective ofthe target current, there may occur a malfunction of the currentsupplied to the front-wheel solenoid 310 being equal to or higher thanthe second reference current. In this case, even when the vehicle speedVv of the motorcycle 1 is equal to or higher than the upward vehiclespeed Vu, the front-wheel displacement amount Lf is decreased to lowerthe vehicle height. In the event of a sudden decrease in the vehicleheight in spite of travel at a speed equal to or higher than the upwardvehicle speed Vu, it becomes difficult for the rider of the motorcycle 1to incline the body and secure a sufficiently large bank angle.

Similarly, in the case of a malfunction of the rear-wheel solenoiddriver 743, even when the vehicle speed Vv of the motorcycle 1 is equalto or higher than the upward vehicle speed Vu, the vehicle height may belowered.

Detail of Malfunction Detector 780

In view of the circumstances described above, the malfunction detector780 according to this embodiment detects a malfunction (such as thedecreasing malfunction) of the actual current of the front-wheelsolenoid 310 and the rear-wheel solenoid being higher than the targetcurrent. Also, when the malfunction occurs, the malfunction detector 780controls the front-wheel passage switch unit 300 and the rear-wheelpassage switch unit 302 so as to maintain the vehicle height.

An exemplary case of the front-wheel side malfunction will now bedescribed in detail, and a rear-wheel side case, which is similar to thefront-wheel side case, will not be elaborated here.

Irrespective of the front-wheel target current being the increasingcurrent for increasing the vehicle height (equal to or higher than thefirst reference current and less than the second reference current) orirrespective of the front-wheel target current being the maintainingcurrent for maintaining the vehicle height (equal to or higher than zeroand less than the first reference current), the malfunction detector 780makes a determination that a malfunction has occurred when the currentdetected by the front-wheel current detector 734 (front-wheel detectioncurrent) is the decreasing current for decreasing the vehicle height(equal to or higher than the second reference current) and when theperiod of time in which the front-wheel displacement amount Lf keepsdecreasing is equal to or longer than the first reference period of timet1. The front-wheel displacement amount Lf is obtained by thefront-wheel displacement amount obtainer 73 based on an output signalfrom the front-wheel relative position detector 281. It is noted thatthe decreasing current is, in other words, a decreasing current fordecreasing the front-wheel displacement amount Lf and the rear-wheeldisplacement amount Lr.

Determining that the malfunction has occurred in the above-describedmanner, the malfunction detector 780 lights the warning lamp and outputsto the relay driver 790 a command signal to turn off the front-wheelrelay 791 so as to maintain the vehicle height. In response to thecommand signal to turn off the front-wheel relay 791 from themalfunction detector 780, the relay driver 790 turns off the front-wheelrelay 791.

FIG. 14B is a time chart illustrating how control is performed by themalfunction detector 780 according to this embodiment. FIG. 14Billustrates how control is performed by the malfunction detector 780 ina case where a malfunction occurs when the front-wheel target current isset to be the maintaining current for maintaining the vehicle heightafter increasing the vehicle height and when the current supplied to thefront-wheel solenoid 310 is controlled to be the set front-wheel targetcurrent.

The malfunction detector 780 makes a determination that the malfunctionhas occurred when the front-wheel detection current is the decreasingcurrent irrespective of the front-wheel target current being themaintaining current and when the period of time in which the front-wheeldisplacement amount Lf keeps decreasing is equal to or longer than thefirst reference period of time t1. Then, in order to maintain thevehicle height, the malfunction detector 780 outputs to the relay driver790 a command signal for turning off the front-wheel relay 791. As aresult, the current stops being supplied to the front-wheel solenoid 310to maintain the front-wheel displacement amount Lf so as to maintain thevehicle height.

Next, using a flowchart, a procedure for the control processingperformed by the malfunction detector 780 will be described.

FIG. 15 is the flowchart of the procedure for the control processingperformed by the malfunction detector 780.

As described above, the malfunction detector 780 detects a malfunctionof the current (actual current) actually flowing to the front-wheelsolenoid 310 and the rear-wheel solenoid being higher than the targetcurrent. In the following description, the control processing fordetecting the malfunction of the front-wheel side will be taken as arepresentative example.

The malfunction detector 780 performs the control processing in everypredetermined cycle (4 msec, for example), repeatedly.

First, the malfunction detector 780 makes a determination as to whetherthe front-wheel target current is the increasing current or themaintaining current, namely, equal to or higher than the first referencecurrent and less than the second reference current or equal to or higherthan zero and less than the first reference current (step S101). Whenthe front-wheel target current is the increasing current or themaintaining current (YES at step S101), the malfunction detector 780makes a determination as to whether the front-wheel detection current isequal to or higher than the decreasing current, namely, equal to orhigher than the second reference current (step S102). When thefront-wheel detection current is equal to or higher than the decreasingcurrent (YES at step S102), the malfunction detector 780 makes adetermination as to whether the front-wheel displacement amount Lfobtained by the front-wheel displacement amount obtainer 73 is becomingsmaller (decreasing) (step S103). This determination is based oncomparison of the last value and the present value of the front-wheeldisplacement amount Lf obtained by the front-wheel displacement amountobtainer 73. When the last value is larger than the present value, themalfunction detector 780 makes a determination as YES. When thefront-wheel displacement amount Lf is decreasing (YES at step S103), thedecreasing current continuation counter is increased (step S104).

Then, the malfunction detector 780 makes a determination as to whetherthe decreasing current continuation counter is equal to or larger than apredetermined first reference value, which is set in advance to beequivalent to the first reference period of time t1 (step S105). Whenthe decreasing current continuation counter is equal to or larger thanthe first reference value (YES at step S105), the malfunction detector780 confirms (determines) that the malfunction has occurred, lights thewarning lamp, and outputs to the relay driver 790 a command signal forturning off the front-wheel relay 791 (step S106). When the decreasingcurrent continuation counter is less than the first reference value (NOat step S105), the malfunction detector 780 ends this processing.

When at step S101 the malfunction detector 780 determines that thefront-wheel target current is not the increasing current or themaintaining current (NO at step S101), when at step S102 the malfunctiondetector 780 determines that the front-wheel detection current is notequal to or higher than the decreasing current (NO at step S102), andwhen at step S103 the malfunction detector 780 determines that thefront-wheel displacement amount Lf is not decreasing (NO at step S103),the decreasing current continuation counter is reset (step S107).

The first reference period of time t1 may be changed in accordance withthe vehicle speed Vv. For example, when the vehicle speed Vv is equal toor higher than 40 km/h, the first reference period of time t1 may be 80msec. As in this example, the first reference period of time t1 may bedecreased as the vehicle speed Vv increases. This is because as thevehicle speed Vv increases, a sudden decrease in the vehicle heightduring travel causes more difficulty in inclining the vehicle body.

Even if there occurs a malfunction of the current (actual current)actually flowing to the front-wheel solenoid 310 and the rear-wheelsolenoid being higher than the target current and this causes thecurrent equal to or higher than the second reference current to start tobe supplied to the front-wheel solenoid 310 and the rear-wheel solenoid,the malfunction detector 780 of the configuration described above turnsoff the front-wheel relay 791 and the rear-wheel relay 792. This stopssupply of the current to the front-wheel solenoid 310 and the rear-wheelsolenoid so as to maintain the front-wheel displacement amount Lf andthe rear-wheel displacement amount Lr. This configuration prevents asudden, undesirably large decrease in the vehicle height even duringtravel at high speed. This, as a result, minimizes the difficulty thatthe rider of the motorcycle has in inclining the vehicle body even if asudden decrease occurs in the vehicle height during travel.

It is noted that the malfunction detector 780 may determine (confirm)that there has occurred the malfunction of the actual current of thefront-wheel solenoid 310 and the rear-wheel solenoid being higher thanthe target current when the current detected by the front-wheel currentdetector 734 and the rear-wheel current detector 744 (front-wheeldetection current and rear-wheel detection current) is equal to orhigher than a predetermined current, which is set to be higher than thethird reference current.

The malfunction detector 780 may determine that the malfunction hasoccurred when one of the following two cases happens first: one casewhere the front-wheel detection current and the rear-wheel detectioncurrent are the decreasing current irrespective of the front-wheeltarget current and the rear-wheel target current being the increasingcurrent or the maintaining current and the period of time in which thefront-wheel displacement amount Lf and the rear-wheel displacementamount Lr are decreasing is equal to or longer than the first referenceperiod of time t1; and the other case where the front-wheel detectioncurrent and the rear-wheel detection current are equal to or higher thanthe predetermined current.

Each of the front-wheel passage switch unit 300 and the rear-wheelpassage switch unit 302 controls, as a single unit, three control modesin accordance with the amount of the current. The three control modesare: increasing mode for increasing the vehicle height, decreasing modefor decreasing the vehicle height, and maintenance mode for maintainingthe vehicle height. In the above-described embodiment, the controlperformed by the malfunction detector 780 is applied to the front-wheelpassage switch unit 300 and the rear-wheel passage switch unit 302 tocontrol the three control modes as a single unit. Application of thecontrol performed by the malfunction detector 780, however, should notbe limited to the units to control the three control modes as a singleunit. The control may be applied to a configuration in which the threecontrol modes are implemented by two control valves (electromagneticactuators).

In controlling a current supplied to a changer (such as anelectromagnetic actuator) to adjust the vehicle height so as to controlthe changer, there may occur a malfunction of the vehicle height beingdecreased from an increased state. When the malfunction of the vehicleheight decrease occurs while the motorcycle is traveling at high speed,there is a possibility of a sudden decrease in the vehicle height inspite of the high-speed travel. This makes it difficult for the rider ofthe motorcycle to incline the body and secure a sufficiently large bankangle.

In a non-limiting embodiment, the changer may include an actuator drivenwhen supplied with a current and capable of changing the relativeposition. The controller may include an actuator driver, a relay, amalfunction detector, and a relay driver. The actuator driver isconfigured to drive the actuator. The relay is configured toelectrically connect the actuator driver and the actuator to each otherand break a connection between the actuator driver and the actuator. Themalfunction detector is configured to detect the decreasing malfunction.The relay driver is configured to shut off the relay when themalfunction detector detects the decreasing malfunction.

In a non-limiting embodiment, the controller may include a targetcurrent setter and a current detector. The target current setter isconfigured to set a target current supplied to the actuator inaccordance with the target value of the relative position. The currentdetector is configured to detect a current supplied to the actuator. Themalfunction detector may be configured to determine that the decreasingmalfunction has occurred when the target current set by the targetcurrent setter is a maintaining current for maintaining the relativeposition or an increasing current for increasing the relative positionand when a detection value detected by the current detector is adecreasing current for decreasing the relative position.

In a non-limiting embodiment, the vehicle height adjustment device mayfurther include a relative position detector configured to detect therelative position. The malfunction detector may be configured todetermine that the decreasing malfunction has occurred when the targetcurrent set by the target current setter is the maintaining current formaintaining the relative position or the increasing current forincreasing the relative position and when the detection value detectedby the current detector is the decreasing current for decreasing therelative position and when a period of time in which the relativeposition detected by the relative position detector keeps decreasing isa predetermined period of time.

In a non-limiting embodiment, the maintaining current may be less than afirst reference current. The increasing current may be equal to orhigher than the first reference current and less than a second referencecurrent, which is set in advance to be higher than the first referencecurrent. The decreasing current may be equal to or higher than thesecond reference current.

In a non-limiting embodiment, the changer may include a spring, anadjustor, a storage chamber, a pump, and an actuator. The springincludes one end supported on a side of the body and includes anotherend supported on a side of the wheel. The adjustor includes anaccommodation chamber to accommodate a fluid and is configured to adjusta length of the spring in accordance with an amount of the fluid in theaccommodation chamber. The storage chamber stores the fluid. The pumpincludes a cylinder and is configured to, when a relative distancebetween the body and the wheel increases, take into the cylinder thefluid stored in the storage chamber and configured to, when the relativedistance between the body and the wheel decreases, discharge the fluidfrom the cylinder. The actuator is driven when supplied with a currentand configured to switch among a state of guiding the fluid dischargedfrom the pump into the accommodation chamber to increase the amount ofthe fluid in the accommodation chamber, a state of guiding the fluid inthe accommodation chamber into the storage chamber to decrease theamount of the fluid in the accommodation chamber, and a state ofmaintaining the amount of the fluid in the accommodation chamber. Whenthe decreasing malfunction occurs causing the vehicle height todecrease, the controller may be configured to maintain the state ofmaintaining the amount of the fluid in the accommodation chamber.

The embodiments eliminate or minimize an undesirably large decrease inthe vehicle height even if a malfunction occurs causing the vehicleheight to decrease during travel.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, thepresent invention may be practiced otherwise than as specificallydescribed herein.

The invention claimed is:
 1. A vehicle height adjustment devicecomprising: a changer configured to change a relative position of a bodyof a vehicle relative to an axle of a wheel of the vehicle; and acontroller configured to control the changer to make the relativeposition a target value so as to control a vehicle height of the body ofthe vehicle, the controller being configured to control the changer tomaintain the relative position irrespective of the target value when adecreasing malfunction occurs causing the vehicle height to decrease;wherein the changer comprises an actuator driven when supplied with acurrent and capable of changing the relative position, and wherein thecontroller comprises: an actuator driver configured to drive theactuator, a relay configured to electrically connect the actuator driverand the actuator to each other and break a connection between theactuator driver and the actuator, a malfunction detector configured todetect the decreasing malfunction, and a relay driver configured to shutoff the relay when the malfunction detector detects the decreasingmalfunction a target current setter configured to set a target currentsupplied to the actuator in accordance with the target value of therelative position, and a current detector configured to detect a currentsupplied to the actuator and wherein the malfunction detector isconfigured to determine that the decreasing malfunction has occurredwhen the target current set by the target current setter is amaintaining current for maintaining the relative position or anincreasing current for increasing the relative position and when adetection value detected by the current detector is a decreasing currentfor decreasing the relative position and wherein the maintaining currentis less than a first reference current, the increasing current is equalto or higher than the first reference current and less than a secondreference current, which is set in advance to be higher than the firstreference current, and the decreasing current is equal to or higher thanthe second reference current.
 2. The vehicle height adjustment deviceaccording to claim 1, further comprising a relative position detectorconfigured to detect the relative position, wherein the malfunctiondetector is configured to determine that the decreasing malfunction hasoccurred when the target current set by the target current setter is themaintaining current for maintaining the relative position or theincreasing current for increasing the relative position and when thedetection value detected by the current detector is the decreasingcurrent for decreasing the relative position and when a period of timein which the relative position detected by the relative positiondetector keeps decreasing is a predetermined period of time.
 3. Thevehicle height adjustment device according to claim 2, wherein thechanger comprises a spring comprising one end supported on a side of thebody and comprising another end supported on a side of the wheel, anadjustor comprising an accommodation chamber to accommodate a fluid andconfigured to adjust a length of the spring in accordance with an amountof the fluid in the accommodation chamber, a storage chamber storing thefluid, a pump comprising a cylinder and configured to, when a relativedistance between the body and the wheel increases, take into thecylinder the fluid stored in the storage chamber and configured to, whenthe relative distance between the body and the wheel decreases,discharge the fluid from the cylinder, and the actuator driven whensupplied with a current and configured to switch among a state ofguiding the fluid discharged from the pump into the accommodationchamber to increase the amount of the fluid in the accommodationchamber, a state of guiding the fluid in the accommodation chamber intothe storage chamber to decrease the amount of the fluid in theaccommodation chamber, and a state of maintaining the amount of thefluid in the accommodation chamber, and wherein when the decreasingmalfunction of a decrease in the vehicle height occurs, the controlleris configured to maintain the state of maintaining the amount of thefluid in the accommodation chamber.
 4. The vehicle height adjustmentdevice according to claim 1, wherein the changer comprises a springcomprising one end supported on a side of the body and comprisinganother end supported on a side of the wheel, an adjustor comprising anaccommodation chamber to accommodate a fluid and configured to adjust alength of the spring in accordance with an amount of the fluid in theaccommodation chamber, a storage chamber storing the fluid, a pumpcomprising a cylinder and configured to, when a relative distancebetween the body and the wheel increases, take into the cylinder thefluid stored in the storage chamber and configured to, when the relativedistance between the body and the wheel decreases, discharge the fluidfrom the cylinder, and the actuator driven when supplied with a currentand configured to switch among a state of guiding the fluid dischargedfrom the pump into the accommodation chamber to increase the amount ofthe fluid in the accommodation chamber, a state of guiding the fluid inthe accommodation chamber into the storage chamber to decrease theamount of the fluid in the accommodation chamber, and a state ofmaintaining the amount of the fluid in the accommodation chamber, andwherein when the decreasing malfunction of a decrease in the vehicleheight occurs, the controller is configured to maintain the state ofmaintaining the amount of the fluid in the accommodation chamber.